Segment Routing (SR) is a source routing technology. The source node selects a path for the packets, and then encodes the path in the packet header as an ordered list of segments. Each segment is identified by the segment identifier (SID). The SR nodes along the path forward the packets based on the SIDs in the packets. Only the source node needs to maintain the path status.

SR can operate with MPLS. In an MPLS network, SR uses MPLS labels as SIDs to forward packets on an LSP.

SR-MPLS characteristics

SR-MPLS has the following characteristics:

· SR-MPLS forwards packets based on the existing MPLS infrastructure. No infrastructure modifications are needed to implement SR on an MPLS network. For more information about the MPLS infrastructure, see MPLS basics configuration in MPLS Configuration Guide.

· SR-MPLS expands and optimizes existing IGPs and BGP and uses the IGPs and BGP to distribute labels.

· SR-MPLS implements network features such as MPLS TE in a simpler way, eliminating issues such as heavy and complicated routing protocol deployment.

Basic concepts

· SR node—A node enabled with the SR-MPLS feature. The ingress node (source node) adds labels to packets. The transit nodes forward packets based on labels. The egress node removes labels and forwards packets to the destination networks. SR nodes form an SR domain.

· Segment—An instruction an SR node executes on the incoming packet.

· SID—Segment ID, which is MPLS label in SR-MPLS.

· Segment type—The following types of segments are available:

¡ Prefix segment—SIDs are assigned to nodes based on destination address prefix. The nodes create prefix-specific forwarding entries.

¡ Adjacency segment—SIDs are assigned to nodes based on adjacency.

· SRLSP—Segment routing label switched path, an LSP along which SR uses MPLS labels as SIDs to forward packets.

· SRGB—Segment routing global block, a range of global labels dedicated for SR-MPLS prefix SIDs. Different nodes can have different SRGBs. The minimum label value of an SRGB label range is referred to as the base value of the SRGB.

· SRLB—Segment routing local block, a range of local labels dedicated for SR-MPLS adjacency SIDs. All nodes share the same SRLB. The minimum label value of the SRLB label range is referred to as the base value of the SRLB.

How SR-MPLS works

SR-MPLS involves the following steps:

1. Label allocation for all nodes and links along the packet forwarding paths.

The following methods are available:

¡ Static segment configuration

¡ Dynamic SID allocation through an IGP

¡ Dynamic SID allocation through BGP

¡ SID allocation through BGP EPE

2. Label forwarding entry installation based on SIDs. All SR-MPLS devices in the SR domain use the allocated labels to create label forwarding entries.

3. SRLSP setup. You can manually configure SRLSPs, or use an IGP, BGP, or a controller to dynamically create SRLSPs.

When the ingress node of an SRLSP receives a packet, it adds labels to the packet and forwards the packet to the egress node through the SRLSP. After receiving a packet from the SRLSP, the egress node removes the label and forwards the packet based on the routing table.

You can bind a higher layer application (for example, MPLS TE) to an SRLSP to forward traffic of the application through the SRLSP.

Static segment configuration

Static SR-MPLS provides the following methods for configuring static segments for a destination:

· Prefix segment method—Manually configure the incoming label, outgoing label, and next hop for the destination address prefix on each SR node.

· Adjacency segment method—Manually configure the incoming label and next hop for the adjacency to the neighbor on each SR node.

Dynamic SID allocation through an IGP

SR-MPLS expands IGP protocols such as IS-IS and OSPF to advertise SIDs in IGP protocol packets. SR-MPLS provides the following methods for dynamically allocating and advertising SIDs:

· Prefix SID.

· Adjacency SID.

Prefix SID

After you configure an SID for the loopback address on each SR node, the SIDs uniquely identify the SR nodes. All SR nodes in the SR domain use an IGP to advertise their own prefix SIDs. After receiving advertised prefix SIDs, each SR node calculates the prefix SIDs to the advertisers.

The prefix SID advertisement can be one of the following types:

· Absolute value advertisement—Each SR node advertises the prefix SID absolute value and the SRGB.

· Index value advertisement—Each SR node advertises the prefix SID index and the SRGB.

Each SR node is assigned a globally unique index value for the node's prefix. The prefix SID an SR node allocates to a prefix equals the SRGB base of the SR node plus the index for that prefix.

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NOTE:

The device supports only the index value advertisement in the current software release.

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Adjacency SID

SR nodes use an IGP to advertise SIDs allocated to the IGP adjacencies (that is, the links to its IGP neighbors). The SIDs are used to identify the links.

The adjacency SIDs can be allocated automatically or manually.

· Automatic adjacency SID allocation—SR nodes allocate labels in SRLBs to the IGP adjacencies as SIDs.

· Manual adjacency SID allocation—You can assign adjacency SIDs by using absolute values or index values. If you use index values, the adjacency SID of a link is the base value of the SRLB plus the index value for the link.

Dynamic SID allocation through BGP

SR-MPLS expands BGP to advertise prefix SIDs in BGP protocol packets. BGP uses routing policies to assign SIDs to prefixes when redistributing routes. The SIDs uniquely identify the SR nodes. All SR nodes in the SR domain use BGP to advertise their own prefix SIDs, including the SIDs and SID index values. From received advertisement packets, each SR node derives the prefix SIDs for the advertisers.

BGP prefix SIDs can be exchanged between BGP peers only through IPv4 unicast routes.

Dynamic SID allocation through BGP applies to MPLS VPN inter-AS option C networks.

SID allocation through BGP EPE

The BGP Egress Peer Engineering (BGP EPE) feature assigns labels to BGP peers to steer traffic across ASs to specific BGP neighbors or links.

After you configure BGP EPE on a device, the device assigns SIDs to connected BGP peers or peer groups to identify the BGP neighbors or links. These SIDs are called BGP peering SIDs or BGP peering segments.

BGP peering segments or SIDs fall into the following types:

· Peer Node Segment (Peer Node SID)—Node type, typically assigned to a BGP neighbor that has used a directly connected interface to establish a BGP session with the device.

· Peer Adjacency Segment (Peer Adjacency SID)—Adjacency type, typically assigned to a BGP neighbor that uses a loopback interface to establish a BGP session with the device.

· Peer Set Segment (Peer Set SID)—Set type, typically assigned to links when multiple equal cost multi-path (ECMP) paths exist between the device and a BGP neighbor.

SIDs that BGP EPE assigns are locally significant. These SIDs are not advertised to other devices and are not affected by route types exchanged between BGP peers.

SID allocation through BGP EPE is typically used for MPLS VPN inter-AS option B.

Label forwarding entry installation based on SIDs

Label forwarding entry installation based on IGP prefix SIDs

Label forwarding entries based on prefix SIDs can be static or dynamic.

· Static label forwarding entries—The device creates local label forwarding entries based on manually configured incoming labels, outgoing labels, and next hops.

· Dynamic label forwarding entries—The device uses the IGP to flood in the SR domain the local SRGB and the index of the prefix SID for the local loopback interface. Based on the flooded information, the other devices in the domain calculates their local label forwarding entries by using the following rules:

¡ Incoming label = Local SRGB base value + Index

¡ Outgoing label = SRGB base value of the next hop + Index

Figure 1 Creating label forwarding entries based on prefix SIDs

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Figure 1 shows how dynamic label forwarding entries are created. After you assign index value 201 to loopback address 1.1.1.1/32 on Device C, Device C uses an IGP packet to advertise the index value and its local SRGB. Then, the devices calculate incoming and outgoing labels according to the previously mentioned label calculation rules.

· Devices C calculates its incoming label, which is 16201.

· Device B calculates its incoming label and outgoing label and creates a label forwarding entry. The incoming label is 16201. The outgoing label is 16201. The next hop is Device C.

· Device A calculates its incoming label and outgoing label and creates a label forwarding entry. The incoming label is 16201. The outgoing label is 16201. The next hop is Device B.

Label forwarding entry installation based on BGP prefix SIDs

The device redistributes routes to BGP and assigns prefix SIDs to redistributed routes based on routing policies. Then, the device uses BGP to flood in the SR domain the prefix SIDs and the indexes of the prefix SIDs. Based on the flooded information, the other devices in the domain calculates their local label forwarding entries by using the following rules:

· Incoming label = Local SRGB base value + Index

· Outgoing label = Received SID

Figure 2 Creating label forwarding entries based on BGP prefix SIDs

Figure 2 shows how label forwarding entries are created. After you assign index value 201 to loopback address 1.1.1.1/32 on Device D, Device D redistributes the route of the address and assigns it an SID (16201 in this example). Then, the device uses a BGP packet to advertise the SID and index value. The devices in the SR domain calculate incoming and outgoing labels according to the previously mentioned label calculation rules and create label forwarding entries.

· Devices D calculates its incoming label, which is 16201.

· Device C calculates its incoming label and outgoing label and creates a label forwarding entry. The incoming label is 16201. The outgoing label is 16201. The next hop is Device D.

· Device B calculates its incoming label and outgoing label and creates a label forwarding entry. The incoming label is 16201. The outgoing label is 16201. The next hop is Device C.

· Device A calculates its incoming label and outgoing label and creates a label forwarding entry. The incoming label is 16201. The outgoing label is 16201. The next hop is Device B.

Label forwarding entry installation based on BGP EPE

Configure BGP EPE on border routers to assign SIDs to specific peers or peer groups.

Figure 3 Creating label forwarding entries by using BGP EPE

As shown in Figure 3, you can configure BGP EPE on Device B to assign BGP peering SIDs to EBGP neighbors Device C and Device D. BGP peering SIDs are locally significant and are not advertised to neighbors.

Label forwarding entry installation based on adjacency SIDs

When using adjacency SIDs, each device allocates a static or dynamic incoming label to the link to its neighbor. The label has local significance. Multiple devices can use the same adjacency SID.

Figure 4 Creating label forwarding entries based on adjacency SIDs

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As shown in Figure 4, the devices are running the same IGP. After IGP adjacencies are established between the devices, Device A, Device B, and Device C allocates labels and creates label forwarding entries as follows:

· Device A allocates label 203 to the link to its neighbor Device B.

· Device B allocates label 202 to the link to its neighbor Device C.

· Device C allocates label 201 to the link to its neighbor Device D.

· Device A creates a label forwarding entry with incoming label 203 and next hop Device B.

· Device B creates a label forwarding entry with incoming label 202 and next hop Device C.

· Device C creates a label forwarding entry with incoming label 201 and next hop Device D.

SRLSP setup

You can use the following methods to create SRLSPs:

· Manually configure an SRLSP.

To configure an SRLSP, you must specify the label stack for packets to be forwarded along the SRLSP on the ingress node. Each label in the stack corresponds to a prefix SID or adjacency SID. The system can look for the outgoing label and next hop based on the prefix SID or adjacency SID.

· Configure SR nodes to use BGP or an IGP to dynamically establish an SRLSP.

SR nodes follow these steps to establish SRLSPs:

a. Use BGP or an IGP to collect prefix SID information from the SR-MPLS network.

b. Calculate the shortest paths to other SR nodes based on the collected prefix SID information and the BGP or IGP network topology.

c. Establish SRLSPs based on the shortest paths.

· Configure a controller to deploy SRLSP configuration to the device so the device creates SRLSPs.

For more information about controller configuration, see the user guide for the controller.

Packet forwarding in MPLS SR

Based on the SID allocation method, SR-MPLS uses one of the following packet forwarding methods:

· Prefix SID-based packet forwarding—The ingress node encapsulates the prefix SID for the egress node to a packet. The transit nodes forward the packet based on label forwarding entries.

· Adjacency SID-based packet forwarding—The ingress node encapsulates the label stack that contains the adjacency SIDs of all links along the forwarding path to a packet. Each transit node uses the top label in the label stack to determine the next hop and pops the top label before forwarding the packet to the next hop.

· Prefix and adjacency SID-based packet forwarding—The nodes use prefix SID-based packet forwarding in combination with adjacency-based packet forwarding.

Prefix SID-based packet forwarding within the same AS

Figure 5 shows how a packet is forwarded along the SRLSP from Device A to Device E based on prefix SIDs. In this example, the outgoing label for the packet is 16201 on Device A.

1. Ingress node Device A searches for a forwarding entry for label 16201, adds outgoing label 16201 to the packet and sends the packet to the next hop (Device B).

2. When transit node Device B receives the packet, it searches for a label forwarding entry that matches the label in the packet. Then, Device B uses the outgoing label of the matched entry (16201) to replace the label in the packet and forwards the packet to the next hop (Device C).

3. Transit nodes Device C and Device D process the packet in the same way Device B does.

4. When egress node Device E receives the packet, it removes the label and forwards the packet by IP address.

Figure 5 Prefix SID-based packet forwarding

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Prefix SID-based packet forwarding across ASs

Figure 6 shows how a packet is forwarded along the SRLSP from Device A to Device D based on prefix SIDs. In this example, the outgoing label for the packet is 16201 on Device A.

1. Ingress node Device A searches for a forwarding entry for label 16201, adds outgoing label 16201 to the packet, and sends the packet to the next hop (Device B).

2. When transit node Device B receives the packet, it searches for a label forwarding entry that matches the label in the packet (16201). Then, Device B uses the outgoing label of the matched entry (16201) to replace the label in the packet and forwards the packet to the next hop (Device C).

3. Transit nodes Device C processes the packet in the same way Device B does.

4. When egress node Device D receives the packet, it removes the label and forwards the packet by IP address.

Figure 6 Prefix SID-based packet forwarding across ASs

BGP EPE-based packet forwarding across ASs

As shown in Figure 7, you can configure BGP EPE and an SRLSP used for the MPLS TE tunnel on Device B to steer packets to travel through Device C or Device D to Device E. In this example, packets travel from Device A through Device B and Device D to Device E. Device B uses BGP EPE to assign SID 6000 to Device D. A static SRLSP is established between Device B and Device D for the MPLS TE tunnel and Device B also assigns SID 6000 to the SRLSP.

1. Within AS 100, source node Device A adds label 16204 to the packet according to the SRLSP, and sends the packet to Device B.

2. When Device B receives the packet, it searches for a label forwarding entry and finds that it should forward the packet through the MPLS TE tunnel. Then, Device B removes label 16204 from the packet, and forwards the packet through the MPLS TE tunnel to Device D.

3. Within AS 200, Device D searches for a label forwarding entry based on the SRLSP, adds label 16201 to the packet, and sends the packet to Device E.

4. When egress node Device E receives the packet, it removes label 16201 and forwards the packet by IP address.

Figure 7 BGP EPE-based packet forwarding across ASs

Adjacency SID-based packet forwarding

Figure 8 shows how a packet is forwarded along the SRLSP from Device A to Device E based on adjacency SIDs. In this example, the label stack for the packet is configured as (200, 201, 202, and 203) on Device A.

1. Ingress node Device A searches for a forwarding entry for the top label (200) to determine the next hop. Then, Device A adds label stack (201, 202, and 203) to the packet, and forwards the packet to the next hop (Device B).

2. When transit node Device B receives the packet, it searches for a forwarding entry for the top label (201) to determine the next hop. Then, Device B removes the top label from the stack and forwards the packet to the next hop (Device C).

3. When transit node Device C receives the packet, it searches for a forwarding entry for the top label (202) to determine the next hop. Then, Device C removes the top label from the stack and forwards the packet to the next hop (Device D).

4. When transit node Device D receives the packet, it searches for a forwarding entry for the label (203) to determine the next hop. Then, Device D removes the label stack from the packet and forwards the packet to the next hop (Device E).

5. When egress node Device E receives the packet, it forwards the packet by IP address.

Figure 8 Adjacency SID-based packet forwarding

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Prefix and adjacency SID-based packet forwarding

Figure 9 shows how a packet is forwarded along the SRLSP from Device A to Device E based on prefix SIDs and adjacency SIDs. In this example, the index value for the prefix SID of Device C is 1. The prefix SIDs for Device A, Device B, and Device C are 16001, 16001, and 16001, respectively. The Adjacency SIDs that Device C and Device D allocate for the adjacent links are 16 and 17, respectively. On Device A, the label stack for the packet is (16001, 16, 17).

1. Ingress node Device A searches for a forwarding entry for label 16001 to determine the outgoing label (16001) and next hop (Device B). Device A swaps label 16001 with 16001. Then, it adds label stack (16001, 16, 17) to the packet and sends the packet to the next hop (Device B).

2. When transit node Device B receives the packet, it searches for a label forwarding entry that matches the top label in the label stack (16001). Then, Device B uses the outgoing label of the matched entry (16001) to replace the top label and forwards the packet to the next hop (Device C).

3. When transit node Device C receives the packet, it removes the top label 16001 and searches for a forwarding entry for the next label (16) to determine the next hop. Then, Device C removes label 16 from the stack and forwards the packet to the next hop (Device D).

4. When transit node Device D receives the packet, it searches for a forwarding entry for the label (17) to determine the next hop. Then, Device D removes the label stack from the packet and forwards the packet to the next hop (Device E).

5. When egress node Device E receives the packet, it forwards the packet by IP address.

Figure 9 Prefix and adjacency SID-based packet forwarding

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IGP SR and LDP interworking

IGP SR and LDP interworking enables SR-MPLS networks and MPLS LDP networks to communicate and cooperate for MPLS forwarding.

SR-MPLS and LDP interworking supports the following modes:

· SR to LDP—Maps prefixes on an LDP network to SR-MPLS SIDs to forward traffic from an SR-MPLS network to an MPLS LDP network.

· LDP to SR—Uses an IGP protocol to advertise SIDs and associates SIDs with LDP labels to forward traffic from an MPLS LDP network to an SR-MPLS network.

· SR over LDP—Enables SR-MPLS networks to communicate through an LDP network.

SR to LDP

The SR to LDP mode defines the following roles:

· Segment Routing Mapping Server (SRMS)—Advertises prefix-SID mappings on behalf of SR-incapable devices (LDP devices). You need to configure prefix-SID mappings on the SRMS.

· Segment Routing Mapping Client (SRMC)—Receives prefix-SID mappings advertised by the SRMS and creates SR-MPLS label forwarding entries.

As shown in Figure 10, Device A and Device B are running SR-MPLS, and Device B, Device C, and Device D are running LDP. After Device D assigns a label for destination address 3.3.3.3/32, Device B and Device C each install an LDP label forwarding entry.

The following steps establish a mapping between the SRLSP and the LDP LSP:

1. Device B acts as an SRMS. It assigns SID index value 201 to the IP address of loopback interface 0 on Device D (3.3.3.3/32), and then advertises an IP prefix-SID mapping TLV to Device A.

2. Device A acts as an SRMC. After receiving the advertised mapping TLV, it creates an SR-MPLS label forwarding entry.

A mapping is established between the SRLSP and the LDP LSP.

Figure 10 SR to LDP packet forwarding

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If Device A uses an SRLSP to send a packet to Device D, the packet is forwarded as follows:

3. Ingress node Device A adds label 16201 to the packet and then sends the packet to transit node Device B.

4. When transit node Device B receives the packet, it searches for a label forwarding entry that matches incoming label 16201. Because the entry does not have an outgoing label, Device B searches for a valid LDP outgoing label for destination address 3.3.3.3/32. Then, Device B adds the LDP label (20) to the packet as the SR outgoing label and forwards the packet to the next hop (Device C).

5. When transit node Device C receives the packet, it searches for an LDP label forwarding entry for incoming label 20. Then, it removes the label from the packet and forwards the packet to egress node Device D.

6. The egress node forwards the packet by IP address.

LDP to SR

As shown in Figure 11, Device C and Device D are running SR-MPLS, and Device A, Device B, and Device C are running LDP. Each device running LDP assigns a label to destination address 3.3.3.3/32 and then installs an LDP label forwarding entry.

The following steps establish an association between the SR-MPLS label and the LDP label:

1. After you assign SID index value 201 to the IP address of loopback interface 0 on Device D (3.3.3.3/32), Device D sends an IGP protocol packet to advertise the index value and the local SRGB.

2. After receiving the packet, Device C creates an SR-MPLS label forwarding entry.

The SR-MPLS label and the LDP label are associated on Device C.

Figure 11 LDP to SR packet forwarding

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A packet from Device A to Device D is forwarded as follows:

3. Ingress node Device A adds an LDP label (20) to the packet and forwards the packets to the next hop (Device B).

4. Device B searches for an LDP label forwarding entry, uses 30 as the outgoing label, and forwards the packet to the next hop (Device C).

5. Device C searches for an LDP label forwarding entry for incoming label 30 and finds no outgoing label. Because valid SR-MPLS outgoing label 16201 exists for the destination address 3.3.3.3.32, Device C uses the label (16201) as the outgoing label and forwards the packet to Device D.

6. Egress node Device D deletes label 16201 from the packet and forwards the packet by IP address.

SR over LDP

For SR-MPLS networks to communicate across an LDP network, the SR/LDP border devices must be able to connect the SR LSP and the LDP LSP as follows:

· SR-MPLS to LDP interworking—The border device installs SR-to-LDP label forwarding entries. For a packet from the SR-MPLS network to the LDP network, the SR-MPLS label forwarding entry on the border device does not have an outgoing label. The border device uses the outgoing label of the LDP label forwarding entry for the same destination address as the outgoing label of the packet.

· LDP to SR-MPLS interworking—The border device installs LDP-to-SR label forwarding entries. For a packet from the LDP network to the SR-MPLS network, the LDP forwarding entry on the border device does not have an outgoing label. The border device must use the outgoing label of the SR-MPLS forwarding entry for the same destination address as the outgoing label of the packet.

Figure 12 SR over LDP diagram

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As shown in Figure 12, Device A, Device B, Device D, and Device E are running SR-MPLS. After you assign index value 201 to loopback interface address 3.3.3.3/32 on Device E, Device E will advertise the index value and the local SRGB. After Device A, Device B, and Device D receive the message, they will install their respective SR-MPLS label forwarding entries. Device B, Device C, and Device D are running LDP. They allocate labels to destination address 3.3.3.3/32 to generate the LDP label forwarding entries.

A packet that Device A sends to Device E will be forwarded as follows:

1. Ingress node Device A encapsulates label 16201 to the packet and forwards the packet to transit node Device B.

2. Transit node Device B searches for an SR-MPLS label forwarding entry for incoming label 16201 and finds that the entry does not have an outgoing label. Because an LDP label forwarding entry with outgoing label 20 exists for the destination address (3.3.3.3/32), Device B encapsulates outgoing label 20 in the packet. Then Device B sends the packet to transit node Device C.

3. Device C forwards the packet to Device D based on its LDP label forwarding entries. The outgoing label is 30.

4. Device D searches for an LDP label forwarding entry for incoming label 30 and finds that the entry does not have an outgoing label. Because an SR-MPLS label forwarding entry with outgoing label 16201 exists for the destination address (3.3.3.3/32), Device B encapsulates outgoing label 16201 in the packet. Then Device D sends the packet to egress node Device E.

5. Egress node Device E deletes the incoming label and forwards the packet by IP address.

BGP SR and LDP interworking

BGP SR and LDP interworking enables SR-MPLS networks that use BGP for SID advertisement to communicate and cooperate with MPLS LDP networks.

To support assigning SIDs to SR-incapable devices in the LDP network, BGP SR and LDP interworking defines the following roles:

· Segment Routing Mapping Server (SRMS)—Advertises prefix-SID mappings on behalf of SR-incapable devices (LDP devices). You must configure prefix-SID mappings on the SRMS.

· Segment Routing Mapping Client (SRMC)—Receives prefix-SID mappings advertised by the SRMS and creates SR-MPLS label forwarding entries.

BGP SR and LDP interworking supports the following modes:

· SR to LDP—Uses BGP IPv4 unicast routes to map prefixes on an LDP network to SR-MPLS SIDs to forward traffic from an SR-MPLS network to an MPLS LDP network.

· LDP to SR—Uses BGP to advertise SIDs and associates SIDs with LDP labels to forward traffic from an MPLS LDP network to an SR-MPLS network.

SR to LDP

When the device uses BGP to implement SR to LDP, it assigns SIDs to the SR-incapable devices in the LDP network according to the locally configured prefix-SID mappings. A node enabled with both SR-MPLS and LDP must act as both an SRMS and an SRMC.

As shown in Figure 13, Device A and Device B are running BGP SR, and Device B, Device C, and Device D are running LDP. After Device D assigns a label for destination address 3.3.3.3/32, Device B, Device C, and Device D each install an LDP label forwarding entry.

The following steps establish a mapping between the SRLSP and the LDP LSP:

1. Acting as an SRMS, Device B assigns SID index value 201 to the IP address of loopback interface 0 on Device D (3.3.3.3/32).

2. Acting as an SRMC, Device B installs an SR label forwarding entry based on the locally configured prefix-SID mapping.

3. Device B establishes a mapping between the SRLSP and the LDP LSP.

4. Device B advertises the prefix SID for 3.3.3.3/32 to Device A through BGP packets. Device A installs an SR label forwarding entry based on the received BGP packets.

Figure 13 BGP SR to LDP packet forwarding

A packet from Device A to Device D is forwarded as follows:

1. Ingress node Device A adds label 16201 to the packet and then sends the packet to transit node Device B.

2. When transit node Device B receives the packet, it searches for an SR label forwarding entry that matches incoming label 16201. Because the entry does not have an outgoing label, Device B searches for a valid LDP outgoing label for destination address 3.3.3.3/32. Then, Device B adds the LDP label (600127) to the packet as the SR outgoing label and forwards the packet to the next hop (Device C).

3. When transit node Device C receives the packet, it searches for an LDP label forwarding entry for incoming label 600127. Then, it removes the label from the packet and forwards the packet to egress node Device D.

4. The egress node forwards the packet by IP address.

LDP to SR

As shown in Figure 14, Device C and Device D are running SR-MPLS, and Device A, Device B, and Device C are running LDP. Each device running LDP assigns a label through LDP to destination address 3.3.3.3/32 and installs an LDP label forwarding entry.

The following steps establish an association between the SR-MPLS label and the LDP label:

1. After you assign SID index value 201 to the IP address of loopback interface 0 on Device D (3.3.3.3/32), Device D uses a BGP IPv4 unicast route to advertise the index value.

2. After receiving the packet, Device C installs an SR label forwarding entry.

The SR label and the LDP label are associated on Device C.

Figure 14 LDP to BGP SR packet forwarding

A packet from Device A to Device D is forwarded as follows:

1. Ingress node Device A adds an LDP label (20) to the packet and forwards the packets to the next hop (Device B).

2. Device B searches for an LDP label forwarding entry, uses 30 as the outgoing label, and forwards the packet to the next hop (Device C).

3. Device C searches for an LDP label forwarding entry for incoming label 30 and finds no outgoing label. Because valid SR-MPLS outgoing label 16201 exists for the destination address 3.3.3.3.32, Device C uses the label (16201) as the outgoing label and forwards the packet to Device D.

4. Egress node Device D deletes label 16201 from the packet and forwards the packet by IP address.

TI-LFA FRR

Topology-Independent Loop-Free Alternate Fast Re-Route (TI-LFA FRR) provides link and node protection. When a link or node fails, TI-LFA FRR switches the traffic to the backup path to ensure continuous data forwarding.

TI-LFA FRR advantages

SR-based TI-LFA FRR has the following advantages:

· It satisfies the basic requirements for IP FRR fast convergence.

· Traffic protection is not affected by the network environment.

· The algorithm is not too complicated.

· It uses the converged route as the backup path. All devices have finished route convergence before the forward process begins.

TI-LFA FRR concepts

· P space—Use the source node of the protected link as the root to establish a shortest path tree. All nodes that are reachable from the source node without passing the protected link form the P space. Nodes in the P space are called P nodes.

· Extended P space—Use the source node of the protected link and its neighbors as the roots to establish shortest path trees. All nodes that are reachable from the source node or one of its neighbors without passing the protected link form the extended P space. The P space is a subset of the extended P space.

· Q space—Use the destination node of the protected link as the root to establish a reverse shortest path tree. All nodes that are reachable from the root node without passing the protected link form the Q space. Nodes in the Q space are called Q nodes.

· TI-LFA algorithm—In real networks, the P space and Q space do not have common nodes or directly connected nodes. The device cannot calculate the backup path and cannot meet the high availability requirement. The TI-LFA algorithm can calculate the extended P space, Q space, converged shortest path tree, repair list, and backup output interface for the protected link to get the backup next hop.

· Repair list—A constraint path used to indicate how a P node reaches a Q node when the P space and Q space do not have common nodes. The repair list contains the following labels (SIDs):

¡ Labels of P nodes.

¡ Adjacency labels from P nodes to Q nodes.

TI-LFA FRR protection types

The following TI-LFA traffic protection types are available:

· Link protection—Protects traffic that traverses a specific link.

· Node protection—Protects traffic that traverses a specific node.

Node protection takes precedence over link protection.

TI-LFA FRR path calculation

As shown in Figure 15, PE 1 is the source node. P 1 is the faulty node. PE 2 is the destination node. The numbers on links represent the link costs. A data flow traverses PE 1, P 1, and PE 2. To protect data against P 1 failure, TI-LFA FRR calculates the extended P space, Q space, shortest path tree converged after P 1 fails, repair list, and backup output interface, and creates the backup forwarding entry.

TI-LFA FRR calculates the backup path by using the following steps:

1. Calculates the extended P space: P 2.

2. Calculates the Q space: PE 2 and P 4.

3. Calculates the shortest path tree converged after P 1 fails: PE 1 --> P 2 --> P 4 --> PE 2.

4. Calculates the repair list: Node label of P 2 (16030), adjacency label of P 2 to P 3 (2168), and adjacency label of P 3 to P 4 (2178).

5. Calculates the backup output interface, that is, the output interface to the next hop after the link from PE 1 to P 1 fails.

Figure 15 TI-LFA FRR diagram

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TI-LFA FRR forwarding process

After TI-LFA FRR finishes backup path calculation, traffic will be switched to the backup path in response to a primary path failure.

As shown in Figure 16, P 2 is a P node and P 4 is a Q node. When the next hop on the primary path (P 1) fails, TI-LFA FRR switches the traffic to the backup path. The following are the detailed steps:

1. PE 1 encapsulates a label stack to a packet according to the repair list. The labels, from the outmost to inmost, are as follows:

¡ Node label of P node P2 (16030), which equals the SRGB base value of P 2 plus the SID index value of P 2.

¡ Adjacency labels from P node P2 to Q node P 4, which are 2168 and 2178.

¡ The destination's node label 16010, which equals the SRGB base value of Q node P 4 plus the SID index value of destination node PE 2.

2. P2 receives the packet, searches for a label forwarding entry based on the outmost label, pops label 2168, and forwards the packet to P 3.

3. P3 receives the packet, searches for a label forwarding entry based on the outmost label, pops label 2178, and forwards the packet to P 4.

4. P4 receives the packet, and searches for a label forwarding entry based on the outmost label. Because the outgoing label is 16010 and the next hop is PE 2, P 4 encapsulates 16010 as the outmost label and forwards the packet to PE 2.

Figure 16 Data forwarding over the TI-LFA FRR backup path

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Microloop avoidance after a network failure

As shown in Figure 17, when Device B fails, traffic to Device C will be switched to the backup path calculated by TI-LFA. After Device A finishes route convergence, traffic will be switched to the post-convergence path. If Device D and Device F have not finished route convergence and still forward traffic along the pre-convergence path, a loop is formed between Device A and Device F. The loop exists until Device D and Device F finish route convergence.

FRR microloop avoidance and SR microloop avoidance can resolve this issue. After you configure TI-LFA, Device A first switches traffic to the backup path calculated by TI-LFA when Device B fails. Then, Device A waits for Device D and Device F to finish route convergence before starting route convergence. After Device A also finishes route convergence, Device A switches the traffic to the converged route.

Figure 17 Diagram for microloop avoidance after a network failure

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Microloop avoidance after a failure recovery

As shown in Figure 18, before the link between Device B and Device C recovers, traffic traverses along the backup path. After the link recovers, Device A will forward the traffic to Device B if Device A finishes route convergence before Device B. Before Device B also finishes route convergence, Device B still forwards the traffic along the backup path. A loop is formed between Device A and Device B.

SR microloop avoidance can resolve this issue. After the link recovers, SR microloop avoidance automatically calculates the optimal path from Device A to Device C and forwards traffic along the path. To forward a packet along the newly calculated path, Device A adds, for example, the adjacency SID from Device B to Device C to the packet and then sends the packet to Device B. Then, Device B forwards the packet to Device C based on the path information.

When the microloop avoidance RIB-update-delay timer expires, Device B should have finished route convergence. Device A does not add path information to packets anymore, and it forwards packets to Device C as usual.

Figure 18 Diagram for microloop avoidance after a failure recovery

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Protocols and standards

· draft-bashandy-rtgwg-segment-routing-ti-lfa-04

· draft-ietf-spring-segment-routing-mpls-00

· draft-ietf-spring-segment-routing-02

· draft-ietf-isis-segment-routing-extensions-06

· draft-ietf-spring-segment-routing-11

· draft-ietf-ospf-segment-routing-extensions-17

· 3draft-ietf-idr-bgpls-segment-routing-epe-15

· draft-ietf-idr-bgp-prefix-sid-19

· RFC 7684, OSPFv2 Prefix/Link Attribute Advertisement

· RFC 7752, North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP

Restrictions and guidelines for MPLS SR

For BGP-based SR, the SRGB range is fixed (16000 through 24000). To use both BGP and an IGP to advertise prefix SIDs, set the SRGB range for MPLS to 16000 through 24000.

SR-MPLS tasks at a glance

IP traffic forwarding over SRLSPs tasks at a glance

To forward IP traffic over SRLSPs, perform the following configuration tasks:

1. Configuring segments

Select one of the following tasks:

¡ Configuring static segments

¡ Configuring IGP-based SID advertisement

2. (Optional.) Configuring the device to prefer SRLSPs in traffic forwarding

3. (Optional.) Configuring SR-MPLS and LDP interworking

¡ Configuring IGP SR and LDP interworking

¡ Configuring BGP SR and LDP interworking

4. (Optional.) Configuring TI-LFA FRR

MPLS TE traffic forwarding over static SRLSPs tasks at a glance

To forward MPLS TE traffic over static SRLSPs, perform the following configuration tasks:

1. Configuring segments

Select one of the following tasks:

¡ Configuring static segments

¡ Configuring IGP-based SID advertisement

¡ Configuring BGP-based SID advertisement

¡ Configuring BGP EPE-based SID allocation

2. Configuring an MPLS TE tunnel to use static SRLSPs

3. (Optional.) Configuring SR-MPLS and LDP interworking

¡ Configuring IGP SR and LDP interworking

¡ Configuring BGP SR and LDP interworking

4. (Optional.) Configuring TI-LFA FRR

MPLS TE traffic forwarding over explicit paths tasks at a glance

To forward MPLS TE traffic over explicit paths, perform the following configuration tasks:

1. Configuring IGP-based SID advertisement

2. Configuring an MPLS TE tunnel over an explicit-path SRLSP

3. (Optional.) Configuring SR-MPLS and LDP interworking

¡ Configuring IGP SR and LDP interworking

¡ Configuring BGP SR and LDP interworking

4. (Optional.) Configuring TI-LFA FRR

MPLS TE traffic forwarding over PCE-calculated SRLSPs tasks at a glance

To forward MPLS TE traffic over PCE-calculated SRLSPs, perform the following configuration tasks:

1. Configuring an MPLS TE tunnel over a PCE-calculated SRLSP

2. (Optional.) Configuring SR-MPLS and LDP interworking

¡ Configuring IGP SR and LDP interworking

¡ Configuring BGP SR and LDP interworking

3. (Optional.) Configuring TI-LFA FRR

Configuring MPLS SRGBs

Restrictions and guidelines

The global MPLS SRGB is used for prefix segments and BGP prefix SIDs. If no MPLS SRGB is configured for a protocol process, the process uses the global MPLS SRGB.

If you have configured prefix SIDs when you configure an SRGB, the SRGB must contain the configured prefix SIDs.

In the following situations, a configured SRGB takes effect after a device reboot:

· The SRGB contains a label that is already used by another protocol. For example, the SRGB contains a label that is already used by LDP.

· The SRGB overlaps with the label range of another protocol. For example, the SRGB for OSPF process 1 overlaps with the SRGB for IS-IS process 1.

Configuring the global MPLS SRGB

1. Enter system view.

system-view

2. Enter segment routing view.

segment-routing

3. Configure the global MPLS SRGB.

global-block minivalue maxivalue

By default, the global MPLS SRGB is from 16000 to 24000.

Configuring the MPLS SRGB for IS-IS

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Configure the MPLS SRGB.

segment-routing global-block minivalue maxivalue

By default, the MPLS SRGB is from 16000 to 24000.

Configuring the MPLS SRGB for OSPF

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Configure the MPLS SRGB.

segment-routing global-block minivalue maxivalue

By default, the MPLS SRGB is from 16000 to 24000.

Configuring the MPLS SRLB

About this task

The segment routing local block (SRLB) is the range of local labels dedicated for SR-MPLS adjacency SIDs.

Restrictions and guidelines

Before configuring the MPLS SRLB, use the display mpls label command to display MPLS label usage information. Make sure that all labels in the specified range are idle. If a label in the range is not idle, the configured MPLS SRLB takes effect only after you save the running configuration and reboot the device. For more information about the display mpls label command, see MPLS Command Reference.

Procedure

1. Enter system view.

system-view

2. Enter segment routing view.

segment-routing

3. Configure the MPLS SRLB.

local-block minimum-value maximum-value

By default, the MPLS SRLB is from 15000 to 15999.

Configuring static segments

Prerequisites

Before you configure static segments for a static SRLSP, perform the following tasks:

· Determine the ingress node, transit nodes, and egress node of the static SRLSP.

· Determine the incoming label for the adjacency segment from a node to next hop of the node. Determine the incoming label of the prefix segment for the destination IP address on each node. On a device, a static SRLSP, a static LSP, and a static CRLSP cannot use the same incoming label. For more information about CRLSP, see MPLS TE configuration in MPLS Configuration Guide.

· Enable MPLS on all nodes and interfaces that will participate in MPLS forwarding. For information about enabling MPLS, see MPLS basics configuration in MPLS Configuration Guide.

Configuring a static adjacency segment

Restrictions and guidelines

This task is required on all nodes of a static SRLSP.

Multiple static SRLSPs can share an adjacency segment.

If you specify the next hop address for a static adjacency segment, make sure the following requirements are met:

· The device has a route to the next hop address.

· MPLS is enabled on the output interface of the route.

If you specify an output interface for a static adjacency segment, make sure the following requirements are met:

· The interface is up.

· The interface can receive direct routes.

· MPLS is enabled on the interface.

A static adjacency segment must use a different incoming label than existing static LSPs, static PWs, and static CRLSPs. If not, the configured adjacency segment is unavailable. The adjacency segment cannot become available even if you change the incoming label of the static LSP, static PW, or static CRLSP. To resolve this problem, you must delete the existing adjacency segment and configure a new one with a different incoming label.

Procedure

1. Enter system view.

system-view

2. Configure a static adjacency segment.

static-sr-mpls adjacency adjacency-path-name in-label label-value { nexthop ip-address | outgoing-interface interface-type interface-number }

The next hop address for a static adjacency segment cannot be a local public IP address.

Configuring a static prefix segment

Restrictions and guidelines

This task is required on all nodes of a static SRLSP.

Multiple static SRLSPs to the same destination can share a prefix segment.

A prefix segment must use the next hop or output interface of the optimal route (non-BGP route) to the destination address of the prefix segment. You can configure multiple prefix segments to the destination address for load sharing if the optimal route has more than one next hop or output interface. To avoid configuration failure, make sure all prefix segments use the same prefix segment name and incoming label.

If you specify only the prefix-path-name argument, the undo static-sr-mpls prefix command deletes all prefix segments with the specified name. If you specify all parameters, only the prefix segment that matches the specified name, destination IP address, and next hop or output interface is deleted.

Procedure

1. Enter system view.

system-view

2. Configure a static prefix segment.

static-sr-mpls prefix prefix-path-name destination ip-address { mask-length | mask } in-label in-label-value [ { nexthop ip-address | outgoing-interface interface-type interface-number } out-label out-label-value ]

The next hop address for a static prefix segment cannot be a local public IP address.

Configuring IGP-based SID advertisement

IGP-based SID advertisement tasks at a glance

GP-based prefix SID advertisement tasks at a glance

Perform the following tasks on each node along an SRLSP:

1. Configuring the IGP to support SR-MPLS

2. Configuring prefix SIDs

3. Configuring MPLS SRGBs

IGP-based adjacency SID advertisement tasks at a glance

Perform the following tasks on each node along an SRLSP:

1. Configuring the IGP to support SR-MPLS

2. Enabling SR-MPLS adjacency label allocation for the IGP

The device will allocate SIDs to adjacencies randomly.

3. (Optional.) Assigning adjacency SIDs

You can assign adjacency SIDs to adjacencies manually.

4. Configuring the MPLS SRLB

Prerequisites for configuring IGP-based SID advertisement

Before you configure IGP-based SID advertisement, perform the following tasks:

· Determine the ingress node, transit nodes, and egress node of an SRLSP.

· Determine the SIDs, MPLS SRGBs, and MPLS SRLBs for nodes.

· Enable MPLS on all nodes and interfaces that will participate in MPLS forwarding. For information about enabling MPLS, see basic MPLS configuration in MPLS Configuration Guide.

Configuring the IGP to support SR-MPLS

Prerequisites

For SR-MPLS to take effect, perform the following tasks before configuring the IGP to support SR-MPLS:

· If the IGP is IS-IS, set the cost style to wide, compatible, or wide-compatible. For more information about the cost style, see IS-IS configuration in Layer 3—IP Routing Configuration Guide.

· If the IGP is OSPF, enable opaque LSA reception and advertisement capability. For more information about the capability, see OSPF configuration in Layer 3—IP Routing Configuration Guide.

Configuring IS-IS to support SR-MPLS

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable SR-MPLS.

segment-routing mpls

By default, SR-MPLS is disabled.

Configuring OSPF to support SR-MPLS

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Enable SR-MPLS.

segment-routing mpls

By default, SR-MPLS is disabled.

Configuring prefix SIDs

About this task

Configuring a prefix SID in loopback interface view binds the SID with the IP address of the loopback interface.

To configure a prefix SID, use one of the following methods:

· Specify an absolute value in the SRGB. The absolute value is used as the prefix SID.

· Specify an index value. The sum of the index value and the SRGB base value is used as the prefix SID. The prefix SID must be in the SRGB.

Restrictions and guidelines

To use a prefix SID for a group of SR nodes in anycast scenarios, specify the n-flag-clear keyword to set the Node-SID flag bit of the prefix SID to 0.

To configure an IS-IS prefix SID, you must enable an IS-IS process on the loopback interface.

A configured OSPF prefix SID takes effect only if the OSPF process enabled on the loopback interface is the same as the OSPF process associated with the prefix SID.

Configuring an IS-IS prefix SID

1. Enter system view.

system-view

2. Enter loopback interface view.

interface loopback interface-number

3. Configure an IS-IS prefix SID.

isis prefix-sid { absolute absolute-value | index index-value } [ n-flag-clear | { explicit-null | no-php } ] *

By default, no IS-IS prefix SID is configured.

Configuring an OSPF prefix SID

1. Enter system view.

system-view

2. Enter loopback interface view.

interface loopback interface-number

3. Configure an OSPF prefix SID.

ospf process-id prefix-sid { absolute absolute-value | index index-value } [ n-flag-clear | { explicit-null | no-php } ] *

By default, no OSPF prefix SID is configured.

Enabling SR-MPLS adjacency label allocation for the IGP

Restrictions and guidelines

For this feature to take effect, you must enable SR-MPLS.

Enabling SR-MPLS adjacency label allocation for IS-IS

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable SR-MPLS adjacency label allocation.

segment-routing adjacency enable

By default, SR-MPLS adjacency label allocation is disabled.

Enabling SR-MPLS adjacency label allocation for OSPF

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Enable SR-MPLS adjacency label allocation.

segment-routing adjacency enable

By default, SR-MPLS adjacency label allocation is disabled.

Assigning adjacency SIDs

About this task

After you enable SR-MPLS adjacency label allocation, the device randomly allocates adjacency SIDs to the links to its IGP neighbors. If the link to an IGP neighbor flaps, the adjacency SID of the link keeps changing. For a link to always use the same adjacency SID, use this feature to assign a specific adjacency SID to the link.

Restrictions and guidelines

To assign adjacency SIDs by using absolute values, make sure the SIDs are in the label range of the SRLB. To assign adjacency SIDs by using index values, make sure the index values plus the base value of the SRLB are in the label range of the SRLB.

The assigned adjacency SIDs take effect after you enable SR-MPLS and SR-MPLS adjacency label allocation.

Prerequisites

Before assigning adjacency SIDs, execute the display mpls label command to display the usage status of the labels that you want to assign as adjacency SIDs. Make sure the labels are in Idle state.

A label that is not in Idle state is being used by another protocol. If you assign it to a link as an adjacency SID, the adjacency SID is not available even if the status of the label changes to Idle later. To use the adjacency SID, you must remove the adjacency SID assignment and assign the adjacency SID again.

Assigning adjacency SIDs to IS-IS adjacencies

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Assign an adjacency SID to an IS-IS adjacency.

isis adjacency-sid { absolute absolute-value | index index-value } [ nexthop nexthop-address ]

By default, an IS-IS adjacency does not have an adjacency SID.

Assigning adjacency SIDs to OSPF adjacencies

1. Enter system view.

system-view

2. Enter interface view.

interface interface-type interface-number

3. Assign an adjacency SID to an OSPF adjacency.

ospf adjacency-sid { absolute absolute-value | index index-value } [ nexthop nexthop-address ]

By default, an OSPF adjacency does not have an adjacency SID.

Configuring BGP-based SID advertisement

BGP-based SID advertisement tasks at a glance

Perform the following tasks on each node along an SRLSP:

1. Configuring BGP to support SR-MPLS

2. Configuring BGP prefix SIDs

3. (Optional.) Specifying the type of label to advertise to the penultimate hop

Prerequisites for configuring BGP-based SID advertisement

Before you configure BGP-based SID advertisement, perform the following tasks:

· Determine the ingress node, transit nodes, and egress node of an SRLSP.

· Determine the index value for the prefix SID of each node:

· Enable MPLS on all nodes and interfaces that will participate in MPLS forwarding. For information about enabling MPLS, see basic MPLS configuration in MPLS Configuration Guide.

Configuring BGP to support SR-MPLS

1. Enter system view.

system-view

2. Enable BGP and enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Create the BGP IPv4 unicast address family and enter its view.

address-family ipv4 [ unicast ]

4. Enable SR-MPLS.

segment-routing mpls

By default, SR-MPLS is disabled.

Configuring BGP prefix SIDs

About this task

To configure a BGP prefix SID, use the following methods:

· Instead of specifying a routing policy for route redistribution, use the SID advertised by the IGP as the BGP prefix SID.

· Specify a routing policy for route redistribution. Set the index value for the prefix SID in the routing policy to define the binding between the SID and the prefix.

Restrictions and guidelines

To use BGP routes to exchange prefix SIDs, you must enable BGP peers to exchange labeled routes.

Configuring the device to use the SIDs advertised by the IGP

1. Configure the IGP to support SR-MPLS.

For more information, see "Configuring the IGP to support SR-MPLS."

2. Configure prefix SIDs.

For more information, see "Configuring prefix SIDs."

3. Enter system view.

system-view

4. Enter BGP instance view.

bgp as-number [ instance instance-name ]

5. Enter BGP IPv4 unicast address family view.

address-family ipv4 [ unicast ]

6. Redistribute routes from IS-IS or OSPF.

import-route { isis | ospf } process-id

Specifying a routing policy for route redistribution

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Enter BGP IPv4 unicast address family view.

address-family ipv4 [ unicast ]

4. Redistribute routes from IS-IS or OSPF and apply a routing policy to the redistributed routes.

import-route { isis | ospf } process-id route-policy route-policy-name

5. Set the index value for the prefix SID:

a. Return to BGP instance view.

quit

b. Return to system view.

quit

c. Enter the routing policy view.

route-policy route-policy-name { deny | permit } node node-number

d. Specify a label index value.

apply label-index index-value

By default, a routing policy does not have a label index value.

Specifying the type of label to advertise to the penultimate hop

Restrictions and guidelines

As a best practice, configure the egress node to advertise an implicit null label to the penultimate hop if the penultimate hop supports PHP.

If you want to simplify packet forwarding on egress but keep labels to determine QoS policies, configure the egress node to advertise an explicit null label to the penultimate hop.

Use non-null labels only in particular scenarios. For example, when OAM is configured on the egress node, the egress node can get the OAM function entity status only through non-null labels. In this case, the egress node assigns an SID to the penultimate hop based on the prefix SID information in the BGP IPv4 unicast route.

If you change the type of label for the device to advertise to the penultimate hop, the device will close all SRLSPs established based on BGP IPv4 unicast routes. Then, the device will re-establish SRLSPs, using the new label type.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Enter BGP IPv4 unicast address family view.

address-family ipv4 [ unicast ]

4. Specify the type of label for the device to advertise to the penultimate hop when the device acts as the egress in an SR-MPLS network.

segment-routing label-advertise { explicit-null | non-null }

By default, the device advertises an implicit null label of 3 to the penultimate hop when it acts as the egress in an SR-MPLS network.

Configuring BGP EPE-based SID allocation

About this task

After you configure BGP EPE on a device, the device assigns SIDs to connected BGP peers or peer groups to identify the BGP neighbors or links.

Restrictions and guidelines

When you configure BGP EPE, follow these restrictions and guidelines:

· By default, a BGP peering SID is node type.

· If you do not specify a routing policy when enabling BGP EPE, the system will assign labels to BGP peers randomly.

· BGP EPE must be used together with SR-MPLS TE policy, MPLS TE, or static SRLSP. When an MPLS TE tunnel is used, the MPLS TE tunnel must use a static SRLSP and the outgoing label of the static SRLSP must be the same as the label specified during BGP EPE configuration.

When you use BGP EPE to apply a routing policy to a peer or peer group, follow these restrictions and guidelines:

· You cannot assign the same label to multiple BGP peers or peer groups.

· You can specify the same routing policy to different BGP peers or peer groups only when you assign a set type label to the BGP peers or peer groups.

· You can use if-match interface as a filtering condition only when you assign adjacency SIDs to BGP peers or peer groups.

Prerequisites

Before assigning BGP-EPE SIDs, execute the display mpls label command to display the usage status of the labels that you want to assign as BGP-EPE SIDs. Make sure the labels are in Idle state. A label that is not in Idle state is being used by another protocol. If you assign it to a peer or peer group as a BGP-EPE SID, the BGP-EPE SID is not available even if the status of the label changes to Idle later. To use the BGP-EPE SID, you must remove the BGP-EPE SID assignment and assign the BGP-EPE SID again.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Enable BGP EPE and specify a routing policy for the peer or peer group.

peer { group-name | ipv4-address [ mask-length ] } egress-engineering [ adjacency | set ] [ route-policy policy-name ]

By default, BGP EPE is disabled.

4. Return to system view.

quit

5. Enter the routing policy view.

route-policy route-policy-name { deny | permit } node node-number

6. Specify a label value.

apply label-value label-value

By default, no label value is specified.

Configuring the device to prefer SRLSPs in traffic forwarding

About this task

This feature enables the device to preferentially use SRLSPs to forward traffic when both SRLSPs and LDP LSPs are available for traffic forwarding. If you do not configure this feature, the device prefers to use LDP LSPs for traffic forwarding.

Restrictions and guidelines

This feature takes effect only when SR-MPLS is enabled and SRLSPs use prefix SIDs.

Configuring the device to prefer SRLSPs established by IS-IS in traffic forwarding

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Configure the device to prefer SRLSPs in traffic forwarding.

segment-routing sr-prefer [ prefix-list prefix-list-name ]

By default, the device prefers LDP LSPs to SRLSPs.

Configuring the device to prefer SRLSPs established by OSPF in traffic forwarding

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Configure the device to prefer SRLSPs in traffic forwarding.

segment-routing sr-prefer [ prefix-list prefix-list-name ]

By default, the device prefers LDP LSPs to SRLSPs.

Configuring an MPLS TE tunnel to use static SRLSPs

Tasks at a glance

1. Enable MPLS TE.

Perform this task on all nodes that the MPLS TE tunnel traverses. For more information, see MPLS TE configuration in MPLS Configuration Guide.

2. Configuring a static SRLSP

Perform this task on the ingress node of the MPLS TE tunnel.

3. Create the tunnel interface and specify the destination address of the tunnel.

Perform this task on the ingress node of the MPLS TE tunnel. For more information, see MPLS TE configuration in MPLS Configuration Guide.

4. Binding a static SRLSP to an MPLS TE tunnel interface

Perform this task on the ingress node of the MPLS TE tunnel.

5. Configure static routes or policy-based routing to direct traffic to the MPLS TE tunnel.

Perform this task on the ingress node of the MPLS TE tunnel. For more information, see MPLS TE configuration in MPLS Configuration Guide.

Configuring a static SRLSP

1. Enter system view.

system-view

2. Configure a static SRLSP.

static-sr-mpls lsp lsp-name out-label out-label-value&<1-n>

Binding a static SRLSP to an MPLS TE tunnel interface

1. Enter system view.

system-view

2. Enter MPLS TE tunnel interface view.

interface tunnel tunnel-number [ mode mpls-te ]

3. Set the MPLS TE tunnel establishment mode to static.

mpls te signaling static

By default, MPLS TE uses RSVP-TE to establish a tunnel.

For more information about this command, see MPLS Command Reference.

4. Bind a static SRLSP to the MPLS TE tunnel interface.

mpls te static-sr-mpls lsp-name [ backup ]

By default, an MPLS TE tunnel does not use a static SRLSP.

The specified SRLSP must be already created by using the static-sr-mpls lsp command.

You can specify the backup keyword to bind a backup static SRLSP only if both the main and backup SRLSPs are established by using the adjacency segment method.

Configuring an MPLS TE tunnel over an explicit-path SRLSP

Tasks at a glance

Perform the following tasks on the ingress node of the MPLS TE tunnel:

1. Configuring an explicit path for the MPLS TE tunnel

2. Creating an MPLS TE tunnel interface and specifying the destination address.

For more information, see MPLS TE configuration in MPLS Configuration Guide.

3. Configuring an MPLS TE tunnel over the explicit path

Prerequisites

Before you configure an MPLS TE tunnel over an explicit-path SRLSP, perform the following tasks:

· Determine the ingress node of the SRLSP.

· Determine the SIDs of the nodes along the SRLSP.

· Enable MPLS on all nodes and interfaces that will participate in MPLS forwarding. For information about enabling MPLS, see basic MPLS configuration in MPLS Configuration Guide.

Configuring an explicit path for the MPLS TE tunnel

1. Enter system view.

system-view

2. Create an explicit path and enter its view.

explicit-path path-name

3. Add or modify a node in the explicit path.

¡ Specify a node by its label.

nextsid [ index index-number ] label label-value type { adjacency | prefix }

For an adjacency or prefix SID node, specify the label assigned to the next hop for the label-value argument.

¡ Specify a node by its IP address.

nexthop [ index index-number ] ip-address [ exclude | include [ loose | strict ] ]

By default, an explicit path does not include any node.

Configuring an MPLS TE tunnel over the explicit path

1. Enter system view.

system-view

2. Enter MPLS TE tunnel interface view.

interface tunnel tunnel-number mode mpls-te

3. Set the MPLS TE tunnel establishment mode to SR.

mpls te signaling segment-routing

By default, MPLS TE uses RSVP-TE to establish a tunnel.

4. Configure the MPLS TE tunnel interface to use an explicit path.

mpls te path preference value explicit-path path-name [ no-cspf ]

By default, MPLS TE uses the calculated path to establish an SRLSP.

Configuring an MPLS TE tunnel over a PCE-calculated SRLSP

Tasks at a glance

1. Enabling MPLS TE

Perform this task on all nodes that the MPLS TE tunnel traverses. For more information, see MPLS TE configuration in MPLS Configuration Guide.

2. Configuring PCE discovery

Perform this task on all nodes that the MPLS TE tunnel traverses. You can manually specify PCEs or configure dynamic PCE discovery. For more information, see MPLS TE configuration in MPLS Configuration Guide.

3. Establishing a PCEP session that supports SR.

Perform this task on all nodes that the MPLS TE tunnel traverses. Set the PCEP device type to active stateful. For more information, see MPLS TE configuration in MPLS Configuration Guide.

4. Creating an MPLS TE tunnel interface and specifying the destination address.

Perform this task on the ingress node of the MPLS TE tunnel. For more information, see MPLS TE configuration in MPLS Configuration Guide.

5. Configuring an MPLS TE tunnel interface to use PCE to calculate the SRLSP

Perform this task on the ingress node of the MPLS TE tunnel.

Configuring an MPLS TE tunnel interface to use PCE to calculate the SRLSP

1. Enter system view.

system-view

2. Enter MPLS TE tunnel interface view.

interface tunnel tunnel-number mode mpls-te

3. Set the MPLS TE tunnel establishment mode to SR.

mpls te signaling segment-routing

By default, MPLS TE uses RSVP-TE to establish a tunnel.

4. Configure the MPLS TE tunnel interface to use PCE to calculate the SRLSP.

¡ Establish an SRLSP by using the path calculated by PCEs.

mpls te path preference value dynamic [ pce [ ip-address ]&<0-8> ]

By default, the automatically calculated path is used to establish an SRLSP.

¡ Establish an SRLSP by using SRLSP delegation.

mpls te delegation

By default, SRLSP delegation is disabled.

Configuring IGP SR and LDP interworking

Restrictions and guidelines for IGP SR and LDP interworking

To configure IGP SR and LDP interworking, make sure the SRLSP uses prefix SIDs.

In the current software version, the SRMS and SRMC devices support only IS-IS-based SR-MPLS.

SR to LDP tasks at a glance

SRMS tasks at a glance

Perform the following tasks on an SRMS:

1. Enabling SR-MPLS on the SRMS:

a. Configuring the IGP to support SR-MPLS

b. Configuring prefix SIDs

c. Configuring MPLS SRGBs

2. Enabling advertisement of locally configured prefix-SID mappings

3. Configuring prefix-SID mappings

SRMC tasks at a glance

Perform the following tasks on each SRMC:

1. Enabling SR-MPLS on the SRMC:

a. Configuring the IGP to support SR-MPLS

b. Configuring prefix SIDs

c. Configuring MPLS SRGBs

2. Enabling reception of advertised prefix-SID mappings

LDP to SR tasks at a glance

1. Configuring the IGP to support SR-MPLS

2. Configuring prefix SIDs

3. Configuring MPLS SRGBs

SR over LDP tasks at a glance

1. Configuring the IGP to support SR-MPLS

2. Configuring prefix SIDs

3. Configuring MPLS SRGBs

Prerequisites for SR-MPLS and LDP internetworking

Before you configure SR-MPLS and LDP internetworking, perform the following tasks:

· Determine the ingress node, transit nodes, and egress node of an SRLSP.

· Determine the index value for the prefix SID of each node.

· Enable MPLS on all nodes and interfaces that will participate in MPLS forwarding. For information about enabling MPLS, see basic MPLS configuration in MPLS Configuration Guide.

Enabling advertisement of locally configured prefix-SID mappings

Restrictions and guidelines

Configure this feature on the device that acts as the SRMS.

Configuring IS-IS to advertise locally configured prefix-SID mappings

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable advertisement of locally configured prefix-SID mappings.

segment-routing mapping-server advertise-local

By default, advertisement is disabled for locally configured prefix-SID mappings.

Configuring OSPF to advertise locally configured prefix-SID mappings

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Enable advertisement of locally configured prefix-SID mappings.

segment-routing mapping-server advertise-local

By default, advertisement is disabled for locally configured prefix-SID mappings.

Configuring prefix-SID mappings

Restrictions and guidelines

Configure this feature on the device that acts as the SRMS.

The specified prefixes must not belong to any existing prefix-SID mappings.

Prerequisites

Before you configure prefix-SID mappings in bulk, plan the number of mappings carefully.

Procedure

1. Enter system view.

system-view

2. Enable SR and enter segment routing view.

segment-routing

3. Configure a prefix-SID mapping.

mapping-server prefix-sid-map ip-address mask-length start-value [ range range-value ] [ attached ]

By default, no prefix-SID mappings exist.

If you specify a value greater than 65535 for the range-value argument, the prefix-SID mappings cannot be advertised through IS-IS or OSPF.

Enabling reception of advertised prefix-SID mappings

Restrictions and guidelines

Configure this feature on the devices that act as the SRMCs.

Configuring IS-IS to receive advertised prefix-SID mappings

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable reception of prefix-SID mappings.

segment-routing mapping-server receive

By default, reception of prefix-SID mappings is enabled.

Configuring OSPF to receive advertised prefix-SID mappings

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Enable reception of prefix-SID mappings.

segment-routing mapping-server receive

By default, reception of prefix-SID mappings is enabled.

Configuring BGP SR and LDP interworking

Restrictions and guidelines for BGP SR and LDP interworking

To configure BGP SR and LDP interworking, make sure the SRLSP uses prefix SIDs.

An SR network node that is enabled with both SR-MPLS and LDP must act as both an SRMS and an SRMC.

SR to LDP tasks at a glance

1. Configuring BGP SR:

¡ Configuring BGP to support SR-MPLS

¡ Configuring BGP prefix SIDs

2. Enabling prefix-SID mappings

3. Configuring prefix-SID mappings

LDP to SR tasks at a glance

1. Configuring BGP to support SR-MPLS

2. Configuring BGP prefix SIDs

Enabling prefix-SID mappings

Restrictions and guidelines

Perform this task on SRMSs.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Enter BGP IPv4 unicast address family view.

address-family ipv4 [ unicast ]

4. Enable prefix-SID mappings.

segment-routing prefix-sid-map

By default, prefix-SID mappings are disabled.

Configuring TI-LFA FRR

Restrictions and guidelines for TI-LFA FRR

TI-LFA FRR is not supported on static SR networks.

In SR-MPLS and LDP interworking scenarios, you must configure the device to prefer the IS-IS or OSPF SRLSP to the LDP LSP. This rule ensures the effectiveness of the TI-LFA FRR backup next hop.

TI-LFA FRR tasks at a glance

1. Enabling TI-LFA FRR

2. (Optional.) Disabling an interface from participating in TI-LFA calculation

On the source node, disable TI-LFA on the route's output interface to the next hop on the primary path.

3. (Optional.) Configuring microloop avoidance

Enabling TI-LFA FRR

Enabling TI-LFA FRR for IS-IS

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable LFA FRR for IS-IS.

fast-reroute lfa [ level-1 | level-2 ]

By default, LFA FRR is disabled for IS-IS.

5. Enable TI-LFA FRR for IS-IS.

fast-reroute ti-lfa [ per-prefix ] [ route-policy route-policy-name | host ] [ level-1 | level-2 ]

By default, TI-LFA FRR is disabled for IS-IS.

Enabling TI-LFA FRR for OSPF

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Enable LFA FRR for OSPF.

fast-reroute { lfa [ abr-only ] | route-policy route-policy-name }

By default, LFA FRR is disabled for OSPF.

4. Enable TI-LFA FRR for OSPF.

fast-reroute ti-lfa [ per-prefix ] [ route-policy route-policy-name | host ]

By default, TI-LFA FRR is disabled for OSPF.

Disabling an interface from participating in TI-LFA calculation

Disabling an IS-IS interface from participating in TI-LFA calculation

1. Enter system view.

system-view

2. Enter the view of IS-IS interface.

interface interface-type interface-number

3. Disable the interface from participating in TI-LFA calculation.

isis fast-reroute ti-lfa disable [ level-1 | level-2 ]

By default, an IS-IS interface participates in TI-LFA calculation.

Disabling an OSPF interface from participating in TI-LFA calculation

1. Enter system view.

system-view

2. Enter the view of OSPF interface.

interface interface-type interface-number

3. Disable the interface from participating in TI-LFA calculation.

ospf fast-reroute ti-lfa disable

By default, an OSPF interface participates in TI-LFA calculation.

Configuring microloop avoidance

About this task

The following microloop avoidance methods are available:

· FRR microloop avoidance—Provides microloop avoidance after a network failure.

On a network deployed with TI-LFA FRR, when a node or link fails, traffic will be switched to the backup path calculated by TI-LFA. If devices on the backup path have not finished route convergence, a loop is formed between the source node (failed node or the previous node along the link) and a device on the backup path. The loop exists until the devices on the backup path finish route convergence.

To resolve this issue, FRR microloop avoidance first switches traffic to the backup path calculated by TI-LFA after the node or link failure. Then, the source node waits for the nodes on the backup path to finish route convergence before starting route convergence.

· SR microloop avoidance—Provides microloop avoidance both after a network failure and after a failure recovery.

After a network failure occurs or recovers, route convergence occurs on relevant network devices. Because of non-simultaneous convergence on network devices, microloops might be formed. After you configure SR microloop avoidance, the devices will forward traffic along the specified path before route convergence is finished on all the relevant network devices. Because the forwarding path is independent of route convergence, microloops are avoided.

To leave sufficient time for IGP to finish route convergence, set the SR microloop avoidance RIB-update-delay timer. Before the timer expires, failure relevant devices will forward traffic along the specified path. After the timer expires, IGP route convergence should have finished and traffic will traverse along the IGP-calculated path.

Restrictions and guidelines

If you configure both FRR microloop avoidance and SR microloop avoidance, SR microloop avoidance takes effect.

Configuring FRR microloop avoidance for IS-IS

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable FRR microloop avoidance for IS-IS.

fast-reroute microloop-avoidance enable [ level-1 | level-2 ]

By default, FRR microloop avoidance is disabled for IS-IS.

5. (Optional.) Set the FRR microloop avoidance RIB-update-delay time.

fast-reroute microloop-avoidance rib-update-delay delay-time [ level-1 | level-2 ]

By default, the FRR microloop avoidance RIB-update-delay time is 5000 ms.

Configuring FRR microloop avoidance for OSPF

1. Enter system view.

system-view

2. Enter OSPF view.

ospf process-id

3. Enable FRR microloop avoidance for OSPF.

fast-reroute microloop-avoidance enable

By default, FRR microloop avoidance is disabled for OSPF.

4. (Optional.) Set the FRR microloop avoidance RIB-update-delay time.

fast-reroute microloop-avoidance rib-update-delay delay-time

By default, the FRR microloop avoidance RIB-update-delay time is 5000 ms.

Configuring SR microloop avoidance for IS-IS

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv4 unicast address family view.

address-family ipv4

4. Enable SR microloop avoidance for IS-IS.

segment-routing microloop-avoidance enable [ level-1 | level-2 ]

By default, SR microloop avoidance is disabled for IS-IS.

5. (Optional.) Set the SR microloop avoidance RIB-update-delay time.

segment-routing microloop-avoidance rib-update-delay delay-time [ level-1 | level-2 ]

By default, the SR microloop avoidance RIB-update-delay time is 5000 ms.

Display and maintenance commands for MPLS SR

Execute display commands in any view.

Task	Command
Display BGP EPE segment information.	display bgp [ instance instance-name ] egress-engineering ipv4 [ ipv4-address ]
Display BGP SR label ranges.	display bgp [ instance instance-name ] segment-routing label-range
Display BGP SR prefix-SID mappings.	display bgp [ instance instance-name ] segment-routing prefix-sid-map [ ip-address mask-length \| verbose ]
Display IS-IS SR adjacency segment information.	display isis segment-routing adjacency [ process-id ]
Display IS-IS SRGB information.	display isis segment-routing global-block [ level-1 \| level-2 ] [ process-id ]
Display IS-IS SR prefix-SID mappings.	display isis segment-routing prefix-sid-map [ active-policy \| backup-policy ] [ process-id ] [ verbose ]
Display static SRLSP and adjacency segment information.	display mpls static-sr-mpls { lsp [ lsp-name ] \| adjacency [ adjacency-path-name ] }
Display static prefix segment information.	display mpls static-sr-mpls prefix [ path lsp-name \| destination ip-address [ mask \| mask-length ] ]
Display OSPF SRGB information.	display ospf [ process-id ] [ area area-id ] segment-routing global-block
Display OSPF SR prefix-SID mappings.	display ospf segment-routing prefix-sid-map [ active-policy \| backup-policy ] [ process-id ] [ verbose ]
Display SR label block information.	display segment-routing label–block [ protocol { isis \| ospf } ]
Display prefix-SID mappings.	display segment-routing mapping-server prefix-sid-map [ ip-address mask-length \| verbose ]

‌

SR-MPLS configuration examples

Example: Configuring an SR-based MPLS TE tunnel over an explicit path

Network configuration

As shown in Figure 19, Router A, Router B, Router C, and Router D are running IS-IS.

Configure dynamic SID allocation on loopback interfaces of the routers. Then, create an explicit path from Router A to Router D and configure the MPLS TE tunnel interface to use SR to establish an MPLS TE tunnel over the explicit path.

Figure 19 Network diagram

‌

Table 1 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Router A	Loop1	1.1.1.1/32	Router B	Loop1	2.2.2.2/32
	GE1/0/1	10.0.0.1/24		GE1/0/1	10.0.0.2/24
				GE1/0/2	11.0.0.1/24
Router C	Loop1	3.3.3.3/32	Router D	Loop1	4.4.4.4/32
	GE1/0/1	11.0.0.2/24		GE1/0/1	12.0.0.2/24
	GE1/0/2	12.0.0.1/24		GE1/0/2	100.1.2.1/24

‌

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure IS-IS on the routers to achieve network level connectivity and set the IS-IS cost style to wide:

# Configure Router A.

<RouterA> system-view

[RouterA] isis 1

[RouterA-isis-1] network-entity 00.0000.0000.0001.00

[RouterA-isis-1] cost-style wide

[RouterA-isis-1] is-level level-1

[RouterA-isis-1] mpls te enable

[RouterA-isis-1] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] isis enable 1

[RouterA-GigabitEthernet1/0/1] quit

[RouterA] interface loopback 1

[RouterA-LoopBack1] isis enable 1

[RouterA-LoopBack1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] network-entity 00.0000.0000.0002.00

[RouterB-isis-1] cost-style wide

[RouterB-isis-1] is-level level-1

[RouterB-isis-1] mpls te enable

[RouterB-isis-1] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] isis enable 1

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] isis enable 1

[RouterB-GigabitEthernet1/0/2] quit

[RouterB] interface loopback 1

[RouterB-LoopBack1] isis enable 1

[RouterB-LoopBack1] quit

# Configure Router C.

<RouterC> system-view

[RouterC] isis 1

[RouterC-isis-1] network-entity 00.0000.0000.0003.00

[RouterC-isis-1] cost-style wide

[RouterC-isis-1] is-level level-1

[RouterC-isis-1] mpls te enable

[RouterC-isis-1] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] isis enable 1

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface gigabitethernet 1/0/2

[RouterC-GigabitEthernet1/0/2] isis enable 1

[RouterC-GigabitEthernet1/0/2] quit

[RouterC] interface loopback 1

[RouterC-LoopBack1] isis enable 1

[RouterC-LoopBack1] quit

# Configure Router D.

<RouterD> system-view

[RouterD] isis 1

[RouterD-isis-1] network-entity 00.0000.0000.0004.00

[RouterD-isis-1] cost-style wide

[RouterD-isis-1] is-level level-1

[RouterD-isis-1] mpls te enable

[RouterD-isis-1] quit

[RouterD] interface gigabitethernet 1/0/1

[RouterD-GigabitEthernet1/0/1] isis enable 1

[RouterD-GigabitEthernet1/0/1] quit

[RouterD] interface gigabitethernet 1/0/2

[RouterD-GigabitEthernet1/0/2] isis enable 1

[RouterD-GigabitEthernet1/0/2] quit

[RouterD] interface loopback 1

[RouterD-LoopBack1] isis enable 1

[RouterD-LoopBack1] quit

3. Configure LSR IDs, and enable MPLS and MPLS TE:

# Configure Router A.

[RouterA] mpls lsr-id 1.1.1.1

[RouterA] mpls te

[RouterA-te] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] mpls enable

[RouterA-GigabitEthernet1/0/1] quit

# Configure Router B.

[RouterB] mpls lsr-id 2.2.2.2

[RouterB] mpls te

[RouterB-te] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] mpls enable

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] mpls enable

[RouterB-GigabitEthernet1/0/2] quit

# Configure Router C.

[RouterC] mpls lsr-id 3.3.3.3

[RouterC] mpls te

[RouterC-te] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] mpls enable

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface gigabitethernet 1/0/2

[RouterC-GigabitEthernet1/0/2] mpls enable

[RouterC-GigabitEthernet1/0/2] quit

# Configure Router D.

[RouterD] mpls lsr-id 4.4.4.4

[RouterD] mpls te

[RouterD-te] quit

[RouterD] interface gigabitethernet 1/0/1

[RouterD-GigabitEthernet1/0/1] mpls enable

[RouterD-GigabitEthernet1/0/1] quit

4. Enable SR-MPLS on the routers:

# Configure Router A.

[RouterA] isis 1

[RouterA-isis-1] address-family ipv4

[RouterA-isis-1-ipv4] segment-routing mpls

[RouterA-isis-1-ipv4] quit

[RouterA-isis-1] quit

# Configure Router B.

[RouterB] isis 1

[RouterB-isis-1] address-family ipv4

[RouterB-isis-1-ipv4] segment-routing mpls

[RouterB-isis-1-ipv4] quit

[RouterB-isis-1] quit

# Configure Router C.

[RouterC] isis 1

[RouterC-isis-1] address-family ipv4

[RouterC-isis-1-ipv4] segment-routing mpls

[RouterC-isis-1-ipv4] quit

[RouterC-isis-1] quit

# Configure Router D.

[RouterD] isis 1

[RouterD-isis-1] address-family ipv4

[RouterD-isis-1-ipv4] segment-routing mpls

[RouterD-isis-1-ipv4] quit

[RouterD-isis-1] quit

5. Configure IS-IS prefix SIDs for the routers:

# Configure Router A.

[RouterA] interface loopback 1

[RouterA-LoopBack1] isis prefix-sid index 10

[RouterA-LoopBack1] quit

# Configure Router B.

[RouterB] interface loopback 1

[RouterB-LoopBack1] isis prefix-sid index 20

[RouterB-LoopBack1] quit

# Configure Router C.

[RouterC] interface loopback 1

[RouterC-LoopBack1] isis prefix-sid index 30

[RouterC-LoopBack1] quit

# Configure Router D.

[RouterD] interface loopback 1

[RouterD-LoopBack1] isis prefix-sid index 40

[RouterD-LoopBack1] quit

6. Configure an explicit path on Router A.

# Create an explicit path to Router D and specify the nodes by their prefix labels.

[RouterA] explicit-path 1

[RouterA-explicit-path-1] nextsid label 16020 type prefix

[RouterA-explicit-path-1] nextsid label 16030 type prefix

[RouterA-explicit-path-1] nextsid label 16040 type prefix

[RouterA-explicit-path-1] quit

7. Configure an MPLS TE tunnel on Router A:

# Configure MPLS TE tunnel interface Tunnel 1.

[RouterA] interface tunnel 1 mode mpls-te

[RouterA-Tunnel1] ip address unnumbered interface LoopBack 1

# Set the tunnel destination address to the IP address of the loopback interface on Router D.

[RouterA-Tunnel1] destination 4.4.4.4

# Configure the MPLS TE tunnel interface to use SR to establish a tunnel over the explicit path.

[RouterA-Tunnel1] mpls te signaling segment-routing

[RouterA-Tunnel1] mpls te path preference 1 explicit-path 1

[RouterA-Tunnel1] quit

Verifying the configuration

# Display MPLS LSP information on Router A.

[RouterA] display mpls lsp

FEC Proto In/Out Label Out Inter/NHLFE/LSINDEX

10.0.0.2 Local -/- GE1/0/1

Tunnel1 Local -/- NHLFE6

1.1.1.1/32 ISIS 16010/- -

2.2.2.2/32 ISIS 16020/3 GE1/0/1

2.2.2.2/32 ISIS -/3 GE1/0/1

3.3.3.3/32 ISIS 16030/16030 GE1/0/1

3.3.3.3/32 ISIS -/16030 GE1/0/1

4.4.4.4/32 ISIS 16040/16040 GE1/0/1

4.4.4.4/32 ISIS -/16040 GE1/0/1

1.1.1.1/1/17700 SR-TE -/16030 GE1/0/1

16040

# Display information about MPLS TE tunnel interface Tunnel 1 on Router A.

[RouterA] display mpls te tunnel-interface tunnel 1

Tunnel Name : Tunnel 1

Tunnel State : Up (Main CRLSP up.

Main Shared-resource CRLSP down.

Backup CRLSP down.)

Tunnel Attributes :

LSP ID : 17700 Tunnel ID : 1

Admin State : Normal

Ingress LSR ID : 1.1.1.1 Egress LSR ID : 4.4.4.4

Signaling : Segment-Routing Static CRLSP Name : -

Resv Style : SE

Tunnel mode : -

Reverse-LSP name : -

Reverse-LSP LSR ID : - Reverse-LSP Tunnel ID: -

Class Type : CT0 Tunnel Bandwidth : 0 kbps

Reserved Bandwidth : 0 kbps

Setup Priority : - Holding Priority : -

Affinity Attr/Mask : 0/0

Explicit Path : 1

Backup Explicit Path : -

Metric Type : TE

Record Route : Disabled Record Label : Disabled

FRR Flag : Disabled Bandwidth Protection : Disabled

Backup Bandwidth Flag: Disabled Backup Bandwidth Type: -

Backup Bandwidth : -

Bypass Tunnel : No Auto Created : No

Route Pinning : Disabled

Retry Limit : 3 Retry Interval : 2 sec

Reoptimization : Disabled Reoptimization Freq : -

Backup Type : None Backup LSP ID : -

Backup Restore Time : -

Auto Bandwidth : Disabled Auto Bandwidth Freq : -

Min Bandwidth : - Max Bandwidth : -

Collected Bandwidth : - Service-Class : -

Traffic Policy : Disable

Path Setup Type : EXPLICIT/-

Last Down Reason : Signal Error

Down Time : 18-11-13 14:34:06:232

# Display the NHLFE entry information.

[RouterA] display mpls forwarding nhlfe

Total NHLFE entries: 3

Flags: T - Forwarded through a tunnel

N - Forwarded through the outgoing interface to the nexthop IP address

B - Backup forwarding information

A - Active forwarding information

M - P2MP forwarding information

NID Tnl-Type Flag OutLabel Forwarding Info

--------------------------------------------------------------------------------

5 LOCAL NA - GE1/0/1 10.0.0.2

6 SRLSP NA 16030 GE1/0/1 10.0.0.2

16040

268435457 TE TA - 6

The output shows that there are two tiers of outgoing labels to the destination. The traffic is forwarded through the explicit path.

Example: Configuring an MPLS TE tunnel over a PCE-calculated SRLSP

Network configuration

As shown in Figure 20, Router A, Router B, Router C, and Router D are running IS-IS.

Configure Router B, Router C, and Router D as PCEs. Configure Router A as a PCC and specify the PCEs for the PCC. Configure Router A to request the PCEs to calculate the path to Router D.

Figure 20 Network diagram

‌

Table 2 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Router A	Loop1	1.1.1.1/32	Router B	Loop1	2.2.2.2/32
	GE1/0/1	10.0.0.1/24		GE1/0/1	10.0.0.2/24
				GE1/0/2	11.0.0.1/24
Router C	Loop1	3.3.3.3/32	Router D	Loop1	4.4.4.4/32
	GE1/0/1	11.0.0.2/24		GE1/0/1	12.0.0.2/24
	GE1/0/2	12.0.0.1/24		GE1/0/2	100.1.2.1/24

‌

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure IS-IS on the routers to achieve network level connectivity and set the IS-IS cost style to wide:

# Configure Router A.

<RouterA> system-view

[RouterA] isis 1

[RouterA-isis-1] network-entity 00.0000.0000.0001.00

[RouterA-isis-1] cost-style wide

[RouterA-isis-1] mpls te enable

[RouterA-isis-1] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] isis enable 1

[RouterA-GigabitEthernet1/0/1] quit

[RouterA] interface loopback 1

[RouterA-LoopBack1] isis enable 1

[RouterA-LoopBack1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] network-entity 00.0000.0000.0002.00

[RouterB-isis-1] cost-style wide

[RouterB-isis-1] mpls te enable

[RouterB-isis-1] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] isis enable 1

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] isis enable 1

[RouterB-GigabitEthernet1/0/2] quit

[RouterB] interface loopback 1

[RouterB-LoopBack1] isis enable 1

[RouterB-LoopBack1] quit

# Configure Router C.

<RouterC> system-view

[RouterC] isis 1

[RouterC-isis-1] network-entity 00.0000.0000.0003.00

[RouterC-isis-1] cost-style wide

[RouterC-isis-1] mpls te enable

[RouterC-isis-1] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] isis enable 1

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface gigabitethernet 1/0/2

[RouterC-GigabitEthernet1/0/2] isis enable 1

[RouterC-GigabitEthernet1/0/2] quit

[RouterC] interface loopback 1

[RouterC-LoopBack1] isis enable 1

[RouterC-LoopBack1] quit

# Configure Router D.

<RouterD> system-view

[RouterD] isis 1

[RouterD-isis-1] network-entity 00.0000.0000.0004.00

[RouterD-isis-1] cost-style wide

[RouterD-isis-1] mpls te enable

[RouterD-isis-1] quit

[RouterD] interface gigabitethernet 1/0/1

[RouterD-GigabitEthernet1/0/1] isis enable 1

[RouterD-GigabitEthernet1/0/1] quit

[RouterD] interface gigabitethernet 1/0/2

[RouterD-GigabitEthernet1/0/2] isis enable 1

[RouterD-GigabitEthernet1/0/2] quit

[RouterD] interface loopback 1

[RouterD-LoopBack1] isis enable 1

[RouterD-LoopBack1] quit

3. Configure LSR IDs, and enable MPLS and MPLS TE:

# Configure Router A.

[RouterA] mpls lsr-id 1.1.1.1

[RouterA] mpls te

[RouterA-te] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] mpls enable

[RouterA-GigabitEthernet1/0/1] mpls te enable

[RouterA-GigabitEthernet1/0/1] quit

# Configure Router B.

[RouterB] mpls lsr-id 2.2.2.2

[RouterB] mpls te

[RouterB-te] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] mpls enable

[RouterB-GigabitEthernet1/0/1] mpls te enable

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] mpls enable

[RouterB-GigabitEthernet1/0/2] mpls te enable

[RouterB-GigabitEthernet1/0/2] quit

# Configure Router C.

[RouterC] mpls lsr-id 3.3.3.3

[RouterC] mpls te

[RouterC-te] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] mpls enable

[RouterC-GigabitEthernet1/0/1] mpls te enable

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface gigabitethernet 1/0/2

[RouterC-GigabitEthernet1/0/2] mpls enable

[RouterC-GigabitEthernet1/0/2] mpls te enable

[RouterC-GigabitEthernet1/0/2] quit

# Configure Router D.

[RouterD] mpls lsr-id 4.4.4.4

[RouterD] mpls te

[RouterD-te] quit

[RouterD] interface gigabitethernet 1/0/1

[RouterD-GigabitEthernet1/0/1] mpls enable

[RouterD-GigabitEthernet1/0/1] mpls te enable

[RouterD-GigabitEthernet1/0/1] quit

4. Enable SR-MPLS on the routers:

# Configure Router A.

[RouterA] isis 1

[RouterA-isis-1] address-family ipv4

[RouterA-isis-1-ipv4] segment-routing mpls

[RouterA-isis-1-ipv4] quit

[RouterA-isis-1] quit

# Configure Router B.

[RouterB] isis 1

[RouterB-isis-1] address-family ipv4

[RouterB-isis-1-ipv4] segment-routing mpls

[RouterB-isis-1-ipv4] quit

[RouterB-isis-1] quit

# Configure Router C.

[RouterC] isis 1

[RouterC-isis-1] address-family ipv4

[RouterC-isis-1-ipv4] segment-routing mpls

[RouterC-isis-1-ipv4] quit

[RouterC-isis-1] quit

# Configure Router D.

[RouterD] isis 1

[RouterD-isis-1] address-family ipv4

[RouterD-isis-1-ipv4] segment-routing mpls

[RouterD-isis-1-ipv4] quit

[RouterD-isis-1] quit

5. Configure Router B, Router C, and Router D as PCEs.

# Configure Router B.

[RouterB] mpls te

[RouterB-te] pce address 2.2.2.2

# Configure Router C.

[RouterC] mpls te

[RouterC-te] pce address 3.3.3.3

# Configure Router D.

[RouterD] mpls te

[RouterD-te] pce address 4.4.4.4

6. Configure Router A as a PCC and specify the PCEs.

# Configure Router A.

[RouterA] mpls te

[RouterA-te] pcep type active-stateful

[RouterA-te] pce static 2.2.2.2

[RouterA-te] pce static 3.3.3.3

[RouterA-te] pce static 4.4.4.4

7. Configure an MPLS TE tunnel on Router A:

# Configure MPLS TE tunnel interface Tunnel 1.

[RouterA] interface tunnel 1 mode mpls-te

[RouterA-Tunnel1] ip address unnumbered interface LoopBack1

# Configure the MPLS TE tunnel interface to use SR and stateful PCE to establish the tunnel over the SRLSP calculated in PCE delegation mode.

[RouterA-Tunnel1] mpls te signaling segment-routing

[RouterA-Tunnel1] mpls te delegation

[RouterA-Tunnel1] destination 4.4.4.4

Verifying the configuration

# Display discovered PCEs on each router. This example uses Router A.

[RouterA] display mpls te pce discovery verbose

PCE address: 2.2.2.2

Discovery methods: Static

Path scopes:

Path scope Preference

Compute intra-area paths 7

Act as PCE for inter-area TE LSP computation 6

Capabilities:

Bidirectional path computation

Support for request prioritization

Support for multiple requests per message

PCE address: 3.3.3.3

Discovery methods: Static

Path scopes:

Path scope Preference

Compute intra-area paths 7

Act as PCE for inter-area TE LSP computation 6

Capabilities:

Bidirectional path computation

Support for request prioritization

Support for multiple requests per message

PCE address: 4.4.4.4

Discovery methods: Static

Path scopes:

Path scope Preference

Compute intra-area paths 7

Act as PCE for inter-area TE LSP computation 6

Capabilities:

Bidirectional path computation

Support for request prioritization

Support for multiple requests per message

# Verify that PCEP sessions have been established on each router. This example uses Router A.

[RouterA] display mpls te pce peer verbose

Peer address: 2.2.2.2

TCP connection : 1.1.1.1:36818 -> 2.2.2.2:4189

Peer type : PCE

Session type : Stateless

Session state : UP

Mastership : Normal

Role : Active

Session up time : 0000 days 00 hours 15 minutes

Session ID : Local 0, Peer 0

Keepalive interval : Local 30 sec, Peer 30 sec

Recommended DeadTimer : Local 120 sec, Peer 120 sec

Tolerance:

Min keepalive interval : 10 sec

Max unknown messages : 5

Request timeout : 10 sec

Capability for Initiate : No

Capability for Segment-Routing: No

Peer address: 3.3.3.3

TCP connection : 1.1.1.1:36821 -> 3.3.3.3:4189

Peer type : PCE

Session type : Stateless

Session state : UP

Mastership : Normal

Role : Active

Session up time : 0000 days 00 hours 13 minutes

Session ID : Local 1, Peer 0

Keepalive interval : Local 30 sec, Peer 30 sec

Recommended DeadTimer : Local 120 sec, Peer 120 sec

Tolerance:

Min keepalive interval : 10 sec

Max unknown messages : 5

Request timeout : 10 sec

Capability for Initiate : No

Capability for Segment-Routing: No

Peer address: 4.4.4.4

TCP connection : 1.1.1.1:36822 -> 4.4.4.4:4189

Peer type : PCE

Session type : Stateless

Session state : UP

Mastership : Normal

Role : Active

Session up time : 0000 days 00 hours 13 minutes

Session ID : Local 2, Peer 0

Keepalive interval : Local 30 sec, Peer 30 sec

Recommended DeadTimer : Local 120 sec, Peer 120 sec

Tolerance:

Min keepalive interval : 10 sec

Max unknown messages : 5

Request timeout : 10 sec

Capability for Initiate : No

Capability for Segment-Routing: No

Example: Configuring SR-MPLS inter-AS option C (I)

Network configuration

As shown in Figure 21, complete the following tasks:

· Start OSPF and enable OSPF-based SR-MPLS on the PEs in the same AS.

· Configure PE 1 and ASBR-PE 1 to exchange labeled IPv4 routes through IBGP.

· Configure PE 2 and ASBR-PE 2 to exchange labeled IPv4 routes through IBGP.

· Establish an MP-EBGP peer relationship between PE 1 and PE 2 to exchange VPNv4 routes.

· Configure ASBR-PE 1 and ASBR-PE 2 to exchange labeled IPv4 routes through EBGP. Enable BGP-based SR-MPLS.

· Configure dynamic SID allocation on loopback interfaces of the devices. Then, establish an SRLSP based on the allocated SIDs and configure an MPLS TE tunnel over the SRLSP to transmit data.

Figure 21 Network diagram

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Table 3 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
PE 1	Loop1	2.2.2.9/32	PE 2	Loop1	5.5.5.9/32
	GE1/0/1	30.0.0.1/24		GE1/0/1	20.0.0.1/24
	GE1/0/5	1.1.1.2/8		GE1/0/5	9.1.1.2/8
ASBR-PE 1	Loop1	3.3.3.9/32	ASBR-PE 2	Loop1	4.4.4.9/32
	GE1/0/5	1.1.1.1/8		GE1/0/5	9.1.1.1/8
	GE1/0/4	11.0.0.2/8		GE1/0/4	11.0.0.1/8
CE 1	GE1/0/1	30.0.0.2/24	CE 2	GE1/0/1	20.0.0.2/24

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure CE 1:

# Assign an IP address to interface GigabitEthernet 1/0/1.

<CE1> system-view

[CE1] interface gigabitethernet 1/0/1

[CE1-GigabitEthernet1/0/1] ip address 30.0.0.2 24

[CE1-GigabitEthernet1/0/1] quit

# Configure PE 1 as an EBGP peer and redistribute the VPN route.

[CE1] bgp 65001

[CE1-bgp-default] peer 30.0.0.1 as-number 100

[CE1-bgp-default] address-family ipv4 unicast

[CE1-bgp-default-ipv4] peer 30.0.0.1 enable

[CE1-bgp-default-ipv4] import-route direct

[CE1-bgp-default-ipv4] quit

[CE1-bgp-default] quit

3. Configure PE 1:

# Start OSPF on PE 1, set the LSR ID, and enable MPLS and MPLS TE.

<PE1> system-view

[PE1] ospf 1 router-id 2.2.2.9

[PE1-ospf-1] quit

[PE1] interface gigabitethernet 1/0/1

[PE1-GigabitEthernet1/0/1] mpls enable

[PE1-GigabitEthernet1/0/1] quit

[PE1] interface gigabitethernet 1/0/5

[PE1-GigabitEthernet1/0/5] ospf 1 area 0

[PE1-GigabitEthernet1/0/5] mpls enable

[PE1-GigabitEthernet1/0/5] quit

[PE1] interface loopback 1

[PE1-LoopBack1] ip address 2.2.2.9 32

[PE1-LoopBack1] ospf 1 area 0

[PE1-LoopBack1] quit

[PE1] mpls lsr-id 2.2.2.9

[PE1] mpls te

[PE1-te] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[PE1] ospf 1

[PE1-ospf-1] segment-routing mpls

[PE1-ospf-1] quit

[PE1] interface loopback 1

[PE1-LoopBack1] ospf 1 prefix-sid index 20

[PE1-LoopBack1] quit

# Create VPN instance vpn1. Configure an RD and both import and export route targets for the VPN instance.

[PE1] ip vpn-instance vpn1

[PE1-vpn-instance-vpn1] route-distinguisher 11:11

[PE1-vpn-instance-vpn1] vpn-target 1:1 2:2 3:3 import-extcommunity

[PE1-vpn-instance-vpn1] vpn-target 3:3 export-extcommunity

[PE1-vpn-instance-vpn1] quit

# Bind VPN instance vpn1 to interface GigabitEthernet 1/0/1 and assign an IP address to the interface.

[PE1] interface gigabitethernet 1/0/1

[PE1-GigabitEthernet1/0/1] ip binding vpn-instance vpn1

[PE1-GigabitEthernet1/0/1] ip address 30.0.0.1 24

[PE1-GigabitEthernet1/0/1] quit

# Start BGP on PE 1.

[PE1] bgp 100

# Enable the capability to exchange labeled routes with IBGP peer 3.3.3.9.

[PE1-bgp-default] peer 3.3.3.9 as-number 100

[PE1-bgp-default] peer 3.3.3.9 connect-interface loopback 1

[PE1-bgp-default] address-family ipv4 unicast

[PE1-bgp-default-ipv4] peer 3.3.3.9 enable

[PE1-bgp-default-ipv4] peer 3.3.3.9 label-route-capability

# Enable SR-MPLS.

[PE1-bgp-default-ipv4] segment-routing mpls

[PE1-bgp-default-ipv4] quit

# Configure the maximum number of hops from PE 1 to EBGP peer 5.5.5.9 as 10.

[PE1-bgp-default] peer 5.5.5.9 as-number 600

[PE1-bgp-default] peer 5.5.5.9 connect-interface loopback 1

[PE1-bgp-default] peer 5.5.5.9 ebgp-max-hop 10

# Configure peer 5.5.5.9 as a VPNv4 peer.

[PE1-bgp-default] address-family vpnv4

[PE1-bgp-default-vpnv4] peer 5.5.5.9 enable

[PE1-bgp-default-vpnv4] quit

# Configure CE 1 as an EBGP peer of PE 1 and install the learned BGP routes in the routing table of the VPN instance.

[PE1-bgp-default] address-family vpnv4

4. Configure ASBR-PE 1:

# Start OSPF on ASBR-PE 1, set the LSR ID, and enable MPLS and MPLS TE.

<ASBR-PE1> system-view

[ASBR-PE1] ospf 1 router-id 3.3.3.9

[ASBR-PE1-ospf-1] quit

[ASBR-PE1] interface gigabitethernet 1/0/4

[ASBR-PE1-GigabitEthernet1/0/4] mpls enable

[ASBR-PE1-GigabitEthernet1/0/4] quit

[ASBR-PE1] interface gigabitethernet 1/0/5

[ASBR-PE1-GigabitEthernet1/0/5] ospf 1 area 0

[ASBR-PE1-GigabitEthernet1/0/5] mpls enable

[ASBR-PE1-GigabitEthernet1/0/5] quit

[ASBR-PE1] interface loopback 1

[ASBR-PE1-LoopBack1] ip address 3.3.3.9 32

[ASBR-PE1-LoopBack1] ospf 1 area 0

[ASBR-PE1-LoopBack1] quit

[ASBR-PE1] mpls lsr-id 3.3.3.9

[ASBR-PE1] mpls te

[ASBR-PE1-te] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[ASBR-PE1] ospf 1

[ASBR-PE1-ospf-1] segment-routing mpls

[ASBR-PE1-ospf-1] quit

[ASBR-PE1] interface loopback 1

[ASBR-PE1-LoopBack1] ospf 1 prefix-sid index 30

[ASBR-PE1-LoopBack1] quit

# Create a routing policy and specify a label index value.

[ASBR-PE1]ip prefix-list 1 permit 2.2.2.9 32

[ASBR-PE1]route-policy policy1 permit node 1

[ASBR-PE1-route-policy-policy1-1] if-match ip address prefix-list 1

[ASBR-PE1-route-policy-policy1-1] apply label-index 20

[ASBR-PE1-route-policy-policy1-1] quit

# Start BGP on ASBR-PE 1. Enable the capability to exchange labeled routes with IBGP peer 2.2.2.9.

[ASBR-PE1] bgp 100

[ASBR-PE1-bgp-default] peer 2.2.2.9 as-number 100

[ASBR-PE1-bgp-default] peer 2.2.2.9 connect-interface loopback 1

[ASBR-PE1-bgp-default] address-family ipv4 unicast

[ASBR-PE1-bgp-default-ipv4] peer 2.2.2.9 enable

[ASBR-PE1-bgp-default-ipv4] peer 2.2.2.9 label-route-capability

# Redistribute routes from OSPF process 1 to BGP and apply the routing policy.

[ASBR-PE1-bgp-default-ipv4] import-route ospf 1 route-policy policy1

# Enable SR-MPLS.

[ASBR-PE1-bgp-default-ipv4] segment-routing mpls

[ASBR-PE1-bgp-default-ipv4] quit

# Enable the capability to exchange labeled routes with EBGP peer 11.0.0.1.

[ASBR-PE1-bgp-default] peer 11.0.0.1 as-number 600

[ASBR-PE1-bgp-default] address-family ipv4 unicast

[ASBR-PE1-bgp-default-ipv4] peer 11.0.0.1 enable

[ASBR-PE1-bgp-default-ipv4] peer 11.0.0.1 label-route-capability

5. Configure ASBR-PE 2:

# Start OSPF on ASBR-PE 2, set the LSR ID, and enable MPLS and MPLS TE.

<ASBR-PE2> system-view

[ASBR-PE2] ospf 1 router-id 4.4.4.9

[ASBR-PE2-ospf-1] quit

[ASBR-PE2] interface gigabitethernet 1/0/4

[ASBR-PE2-GigabitEthernet1/0/4] mpls enable

[ASBR-PE2-GigabitEthernet1/0/4] quit

[ASBR-PE2] interface gigabitethernet 1/0/5

[ASBR-PE2-GigabitEthernet1/0/5] ospf 1 area 0

[ASBR-PE2-GigabitEthernet1/0/5] mpls enable

[ASBR-PE2-GigabitEthernet1/0/5] quit

[ASBR-PE2] interface loopback 1

[ASBR-PE2-LoopBack1] ip address 4.4.4.9 32

[ASBR-PE2-LoopBack1] ospf 1 area 0

[ASBR-PE2-LoopBack1] quit

[ASBR-PE2] mpls lsr-id 4.4.4.9

[ASBR-PE2] mpls te

[ASBR-PE2-te] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[ASBR-PE2] ospf 1

[ASBR-PE2-ospf-1] segment-routing mpls

[ASBR-PE2-ospf-1] quit

[ASBR-PE2] interface loopback 1

[ASBR-PE2-LoopBack1] ospf 1 prefix-sid index 40

[ASBR-PE2-LoopBack1] quit

# Create a routing policy and specify a label index value.

[ASBR-PE2]ip prefix-list 1 permit 5.5.5.9 32

[ASBR-PE2] route-policy policy1 permit node 1

[ASBR-PE2-route-policy-policy1-1] if-match ip address prefix-list 1

[ASBR-PE2-route-policy-policy1-1] apply label-index 50

[ASBR-PE2-route-policy-policy1-1] quit

# Start BGP on ASBR-PE 2. Enable the capability to exchange labeled routes with IBGP peer 5.5.5.9.

[ASBR-PE2] bgp 600

[ASBR-PE2-bgp-default] peer 5.5.5.9 as-number 600

[ASBR-PE2-bgp-default] peer 5.5.5.9 connect-interface loopback 1

[ASBR-PE2-bgp-default] address-family ipv4 unicast

[ASBR-PE2-bgp-default-ipv4] peer 5.5.5.9 enable

[ASBR-PE2-bgp-default-ipv4] peer 5.5.5.9 label-route-capability

# Redistribute routes from OSPF process 1 to BGP and apply the routing policy.

[ASBR-PE2-bgp-default-ipv4] import-route ospf 1 route-policy policy1

# Enable SR-MPLS.

[ASBR-PE2-bgp-default-ipv4] segment-routing mpls

[ASBR-PE2-bgp-default-ipv4] quit

# Enable the capability to exchange labeled routes with EBGP peer 11.0.0.2.

[ASBR-PE2-bgp-default] peer 11.0.0.2 as-number 100

[ASBR-PE2-bgp-default] address-family ipv4 unicast

[ASBR-PE2-bgp-default-ipv4] peer 11.0.0.2 enable

[ASBR-PE2-bgp-default-ipv4] peer 11.0.0.2 label-route-capability

6. Configure PE 2:

# Start OSPF on PE 2, set the LSR ID, and enable MPLS and MPLS TE.

<PE2> system-view

[PE2] ospf 1 router-id 5.5.5.9

[PE2-ospf-1] quit

[PE2] interface gigabitethernet 1/0/1

[PE2-GigabitEthernet1/0/1] mpls enable

[PE2-GigabitEthernet1/0/1] quit

[PE2] interface gigabitethernet 1/0/5

[PE2-GigabitEthernet1/0/5] ospf 1 area 0

[PE2-GigabitEthernet1/0/5] mpls enable

[PE2-GigabitEthernet1/0/5] quit

[PE2] interface loopback 1

[PE2-LoopBack1] ip address 5.5.5.9 32

[PE2-LoopBack1] ospf 1 area 0

[PE2-LoopBack1] quit

[PE2] mpls lsr-id 5.5.5.9

[PE2] mpls te

[PE2-te] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[PE2] ospf 1

[PE2-ospf-1] segment-routing mpls

[PE2-ospf-1] quit

[PE2] interface loopback 1

[PE2-LoopBack1] ospf 1 prefix-sid index 50

[PE2-LoopBack1] quit

# Create VPN instance vpn1, and configure the RD and route target attributes.

[PE2] ip vpn-instance vpn1

[PE2-vpn-instance-vpn1] route-distinguisher 11:11

[PE2-vpn-instance-vpn1] vpn-target 1:1 2:2 3:3 import-extcommunity

[PE2-vpn-instance-vpn1] vpn-target 3:3 export-extcommunity

[PE2-vpn-instance-vpn1] quit

# Associate GigabitEthernet 1/0/1 with VPN instance vpn1, and assign an IP address to the interface.

[PE2] interface gigabitethernet 1/0/1

[PE2-GigabitEthernet1/0/1] ip binding vpn-instance vpn1

[PE2-GigabitEthernet1/0/1] ip address 20.0.0.1 24

[PE2-GigabitEthernet1/0/1] quit

# Start BGP on PE 2.

[PE2] bgp 600

# Enable the capability to exchange labeled routes with IBGP peer 4.4.4.9.

[PE2-bgp-default] peer 4.4.4.9 as-number 600

[PE2-bgp-default] peer 4.4.4.9 connect-interface loopback 1

[PE2-bgp-default] address-family ipv4 unicast

[PE2-bgp-default-ipv4] peer 4.4.4.9 enable

[PE2-bgp-default-ipv4] peer 4.4.4.9 label-route-capability

# Enable SR-MPLS.

[PE2-bgp-default-ipv4] segment-routing mpls

[PE2-bgp-default-ipv4] quit

# Configure the maximum number of hops from PE 2 to EBGP peer 2.2.2.9 as 10.

[PE2-bgp-default] peer 2.2.2.9 as-number 100

[PE2-bgp-default] peer 2.2.2.9 connect-interface loopback 1

[PE2-bgp-default] peer 2.2.2.9 ebgp-max-hop 10

# Configure peer 2.2.2.9 as a VPNv4 peer.

[PE2-bgp-default] address-family vpnv4

[PE2-bgp-default-vpnv4] peer 2.2.2.9 enable

[PE2-bgp-default-vpnv4] quit

# Configure CE 2 as an EBGP peer and install the learned BGP route in the routing table of the VPN instance.

[PE2-bgp-default] ip vpn-instance vpn1

[PE2-bgp-default-vpn1] peer 20.0.0.2 as-number 65002

[PE2-bgp-default-vpn1] address-family ipv4 unicast

[PE2-bgp-default-ipv4-vpn1] peer 20.0.0.2 enable

7. Configure CE 2:

# Assign an IP address to interface GigabitEthernet 1/0/1.

<CE2> system-view

[CE2] interface gigabitethernet 1/0/1

[CE2-GigabitEthernet1/0/1] ip address 20.0.0.2 24

[CE2-GigabitEthernet1/0/1] quit

# Establish an EBGP peer relationship with PE 2, and redistribute VPN routes.

[CE2] bgp 65002

[CE2-bgp-default] peer 20.0.0.1 as-number 600

[CE2-bgp-default] address-family ipv4 unicast

[CE2-bgp-default-ipv4] peer 20.0.0.1 enable

[CE2-bgp-default-ipv4] import-route direct

Verifying the configuration

# Execute the display ip routing-table command on CE 1 and CE 2 to verify that they have a route to each other. (Details not shown.)

# Verify that CE 1 and CE 2 can ping each other. (Details not shown.)

# Display MPLS LSP information on PE 1.

[PE1] display mpls lsp

FEC Proto In/Out Label Out Inter/NHLFE/LSINDEX

2.2.2.9/32 BGP -/16020 NHLFE1

5.5.5.9/32 BGP -/16050 NHLFE1

5.5.5.9 BGP -/- GE1/0/5

1.1.1.1 Local -/- GE1/0/5

2.2.2.9/32 OSPF 16020/- -

3.3.3.9/32 OSPF 16030/3 GE1/0/5

3.3.3.9/32 OSPF -/3 GE1/0/5

Example: Configuring SR-MPLS inter-AS option C (II)

Network configuration

As shown in Figure 22, complete the following tasks:

· Start OSPF and enable OSPF-based SR-MPLS on the PEs in the same AS.

· Configure PE 1 and ASBR-PE 1 to exchange labeled IPv4 routes through IBGP. Enable BGP-based SR-MPLS.

· Configure PE 2 and ASBR-PE 2 to exchange labeled IPv4 routes through IBGP. Enable BGP-based SR-MPLS.

· Establish an MP-EBGP peer relationship between PE 1 and PE 2 to exchange VPNv4 routes.

· Configure ASBR-PE 1 and ASBR-PE 2 to exchange labeled IPv4 routes through EBGP. Enable BGP-based SR-MPLS.

· Configure dynamic SID allocation on loopback interfaces of the devices. Then, establish an SRLSP based on the allocated SIDs and configure an MPLS TE tunnel over the SRLSP to transmit data.

Figure 22 Network diagram

‌

Table 4 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
PE 1	Loop1	2.2.2.9/32	PE 2	Loop1	5.5.5.9/32
	GE1/0/1	30.0.0.1/24		GE1/0/1	20.0.0.1/24
	GE1/0/5	1.1.1.2/8		GE1/0/5	9.1.1.2/8
ASBR-PE 1	Loop1	3.3.3.9/32	ASBR-PE 2	Loop1	4.4.4.9/32
	GE1/0/5	1.1.1.1/8		GE1/0/5	9.1.1.1/8
	GE1/0/4	11.0.0.2/8		GE1/0/4	11.0.0.1/8
CE 1	GE1/0/1	30.0.0.2/24	CE 2	GE1/0/1	20.0.0.2/24

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure CE 1:

# Assign an IP address to interface GigabitEthernet 1/0/1.

<CE1> system-view

[CE1] interface gigabitethernet 1/0/1

[CE1-GigabitEthernet1/0/1] ip address 30.0.0.2 24

[CE1-GigabitEthernet1/0/1] quit

# Establish an EBGP peer relationship with PE 1, and redistribute VPN routes.

[CE1] bgp 65001

[CE1-bgp-default] peer 30.0.0.1 as-number 100

[CE1-bgp-default] address-family ipv4 unicast

[CE1-bgp-default-ipv4] peer 30.0.0.1 enable

[CE1-bgp-default-ipv4] import-route direct

[CE1-bgp-default-ipv4] quit

[CE1-bgp-default] quit

3. Configure PE 1:

# Start OSPF on PE 1, set the LSR ID, and enable MPLS and MPLS TE.

<PE1> system-view

[PE1] ospf 1 router-id 2.2.2.9

[PE1-ospf-1] quit

[PE1] interface gigabitethernet 1/0/1

[PE1-GigabitEthernet1/0/1] ospf 1 area 0

[PE1-GigabitEthernet1/0/1] mpls enable

[PE1-GigabitEthernet1/0/1] quit

[PE1] interface loopback 1

[PE1-LoopBack1] ip address 2.2.2.9 32

[PE1-LoopBack1] ospf 1 area 0

[PE1-LoopBack1] quit

[PE1] mpls lsr-id 2.2.2.9

[PE1] mpls te

[PE1-te] quit

# Assign an IP address to GigabitEthernet 1/0/5. Start OSPF and enable MPLS on the interface.

[PE1] interface gigabitethernet 1/0/5

[PE1-GigabitEthernet1/0/5] ip address 1.1.1.2 255.0.0.0

[PE1-GigabitEthernet1/0/5] ospf 1 area 0

[PE1-GigabitEthernet1/0/5] mpls enable

[PE1-GigabitEthernet1/0/5] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[PE1] ospf 1

[PE1-ospf-1] segment-routing mpls

[PE1-ospf-1] quit

[PE1] interface loopback 1

[PE1-LoopBack1] ospf 1 prefix-sid index 20

[PE1-LoopBack1] quit

# Create VPN instance vpn1, and configure the RD and route target attributes.

[PE1] ip vpn-instance vpn1

[PE1-vpn-instance-vpn1] route-distinguisher 11:11

[PE1-vpn-instance-vpn1] vpn-target 1:1 2:2 3:3 import-extcommunity

[PE1-vpn-instance-vpn1] vpn-target 3:3 export-extcommunity

[PE1-vpn-instance-vpn1] quit

# Associate GigabitEthernet 1/0/1 with VPN instance vpn1, and assign an IP address to the interface.

[PE1] interface gigabitethernet 1/0/1

[PE1-GigabitEthernet1/0/1] ip binding vpn-instance vpn1

[PE1-GigabitEthernet1/0/1] ip address 30.0.0.1 24

[PE1-GigabitEthernet1/0/1] quit

# Create a routing policy and specify a label index value.

[PE1] route-policy policy1 permit node 1

[PE1-route-policy-policy1-1] apply label-index 20

[PE1-route-policy-policy1-1] quit

# Start BGP on PE 1.

[PE1] bgp 100

# Enable the capability to exchange labeled routes with IBGP peer 3.3.3.9.

[PE1-bgp-default] peer 3.3.3.9 as-number 100

[PE1-bgp-default] peer 3.3.3.9 connect-interface loopback 1

[PE1-bgp-default] address-family ipv4 unicast

[PE1-bgp-default-ipv4] peer 3.3.3.9 enable

[PE1-bgp-default-ipv4] peer 3.3.3.9 label-route-capability

# Enable SR-MPLS.

[PE1-bgp-default-ipv4] segment-routing mpls

# Redistribute the route of loopback interface 1 to BGP and apply the routing policy.

[PE1-bgp-default-ipv4] network 2.2.2.9 32 route-policy policy1

[PE1-bgp-default-ipv4] quit

# Configure the maximum number of hops from PE 1 to EBGP peer 5.5.5.9 as 10.

[PE1-bgp-default] peer 5.5.5.9 as-number 600

[PE1-bgp-default] peer 5.5.5.9 connect-interface loopback 1

[PE1-bgp-default] peer 5.5.5.9 ebgp-max-hop 10

# Configure peer 5.5.5.9 as a VPNv4 peer.

[PE1-bgp-default] address-family vpnv4

[PE1-bgp-default-vpnv4] peer 5.5.5.9 enable

[PE1-bgp-default-vpnv4] quit

# Configure CE 1 as an EBGP peer of PE 1 and install the learned BGP routes in the routing table of the VPN instance.

[PE1-bgp-default] ip vpn-instance vpn1

[PE1-bgp-default-vpn1] peer 30.0.0.2 as-number 65001

[PE1-bgp-default-vpn1] address-family ipv4 unicast

[PE1-bgp-default-ipv4-vpn1] peer 30.0.0.2 enable

4. Configure ASBR-PE 1:

# Start OSPF on ASBR-PE 1, set the LSR ID, and enable MPLS and MPLS TE.

<ASBR-PE1> system-view

[ASBR-PE1] ospf 1 router-id 3.3.3.9

[ASBR-PE1-ospf-1] quit

[ASBR-PE1] interface gigabitethernet 1/0/4

[ASBR-PE1-GigabitEthernet1/0/4] mpls enable

[ASBR-PE1-GigabitEthernet1/0/4] quit

[ASBR-PE1] interface gigabitethernet 1/0/5

[ASBR-PE1-GigabitEthernet1/0/5] ospf 1 area 0

[ASBR-PE1-GigabitEthernet1/0/5] mpls enable

[ASBR-PE1-GigabitEthernet1/0/5] quit

[ASBR-PE1] interface loopback 1

[ASBR-PE1-LoopBack1] ip address 3.3.3.9 32

[ASBR-PE1-LoopBack1] ospf 1 area 0

[ASBR-PE1-LoopBack1] quit

[ASBR-PE1] mpls lsr-id 3.3.3.9

[ASBR-PE1] mpls te

[ASBR-PE1-te] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[ASBR-PE1] ospf 1

[ASBR-PE1-ospf-1] segment-routing mpls

[ASBR-PE1-ospf-1] quit

[ASBR-PE1] interface loopback 1

[ASBR-PE1-LoopBack1] ospf 1 prefix-sid index 30

[ASBR-PE1-LoopBack1] quit

# Start BGP on ASBR-PE 1. Enable the capability to exchange labeled routes with IBGP peer 2.2.2.9.

[ASBR-PE1] bgp 100

[ASBR-PE1-bgp-default] peer 2.2.2.9 as-number 100

[ASBR-PE1-bgp-default] peer 2.2.2.9 connect-interface loopback 1

[ASBR-PE1-bgp-default] address-family ipv4 unicast

[ASBR-PE1-bgp-default-ipv4] peer 2.2.2.9 enable

[ASBR-PE1-bgp-default-ipv4] peer 2.2.2.9 label-route-capability

# Enable SR-MPLS.

[ASBR-PE1-bgp-default-ipv4] segment-routing mpls

[ASBR-PE1-bgp-default-ipv4] quit

# Enable the capability to exchange labeled routes with EBGP peer 11.0.0.1.

[ASBR-PE1-bgp-default] peer 11.0.0.1 as-number 600

[ASBR-PE1-bgp-default] address-family ipv4 unicast

[ASBR-PE1-bgp-default-ipv4] peer 11.0.0.1 enable

[ASBR-PE1-bgp-default-ipv4] peer 11.0.0.1 label-route-capability

5. Configure ASBR-PE 2:

# Start OSPF on ASBR-PE 2, set the LSR ID, and enable MPLS and MPLS TE.

<ASBR-PE2> system-view

[ASBR-PE2] ospf 1 router-id 4.4.4.9

[ASBR-PE2-ospf-1] quit

[ASBR-PE2] interface gigabitethernet 1/0/4

[ASBR-PE2-GigabitEthernet1/0/4] mpls enable

[ASBR-PE2-GigabitEthernet1/0/4] quit

[ASBR-PE2] interface gigabitethernet 1/0/5

[ASBR-PE2-GigabitEthernet1/0/5] ospf 1 area 0

[ASBR-PE2-GigabitEthernet1/0/5] mpls enable

[ASBR-PE2-GigabitEthernet1/0/5] quit

[ASBR-PE2] interface loopback 1

[ASBR-PE2-LoopBack1] ip address 4.4.4.9 32

[ASBR-PE2-LoopBack1] ospf 1 area 0

[ASBR-PE2-LoopBack1] quit

[ASBR-PE2] mpls lsr-id 4.4.4.9

[ASBR-PE2] mpls te

[ASBR-PE2-te] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[ASBR-PE2] ospf 1

[ASBR-PE2-ospf-1] segment-routing mpls

[ASBR-PE2-ospf-1] quit

[ASBR-PE2] interface loopback 1

[ASBR-PE2-LoopBack1] ospf 1 prefix-sid index 40

[ASBR-PE2-LoopBack1] quit

# Start BGP on ASBR-PE 2. Enable the capability to exchange labeled routes with IBGP peer 5.5.5.9.

[ASBR-PE2] bgp 600

[ASBR-PE2-bgp-default] peer 5.5.5.9 as-number 600

[ASBR-PE2-bgp-default] peer 5.5.5.9 connect-interface loopback 1

[ASBR-PE2-bgp-default] address-family ipv4 unicast

[ASBR-PE2-bgp-default-ipv4] peer 5.5.5.9 enable

[ASBR-PE2-bgp-default-ipv4] peer 5.5.5.9 label-route-capability

# Enable SR-MPLS.

[ASBR-PE2-bgp-default-ipv4] segment-routing mpls

[ASBR-PE2-bgp-default-ipv4] quit

# Enable the capability to exchange labeled routes with EBGP peer 11.0.0.2.

[ASBR-PE2-bgp-default] peer 11.0.0.2 as-number 100

[ASBR-PE2-bgp-default] address-family ipv4 unicast

[ASBR-PE2-bgp-default-ipv4] peer 11.0.0.2 enable

[ASBR-PE2-bgp-default-ipv4] peer 11.0.0.2 label-route-capability

6. Configure PE 2:

# Start OSPF on PE 2, set the LSR ID, and enable MPLS and MPLS TE.

<PE2> system-view

[PE2] ospf 1 router-id 5.5.5.9

[PE2-ospf-1] quit

[PE2] interface gigabitethernet 1/0/1

[PE2-GigabitEthernet1/0/1] ospf 1 area 0

[PE2-GigabitEthernet1/0/1] mpls enable

[PE2-GigabitEthernet1/0/1] quit

[PE2] interface loopback 1

[PE2-LoopBack1] ip address 5.5.5.9 32

[PE2-LoopBack1] ospf 1 area 0

[PE2-LoopBack1] quit

[PE2] mpls lsr-id 5.5.5.9

[PE2] mpls te

[PE2-te] quit

# Assign an IP address to GigabitEthernet 1/0/5. Start OSPF and enable MPLS on the interface.

[PE2] interface gigabitethernet 1/0/5

[PE2-GigabitEthernet1/0/5] ip address 9.1.1.2 255.0.0.0

[PE2-GigabitEthernet1/0/5] ospf 1 area 0

[PE2-GigabitEthernet1/0/5] mpls enable

[PE2-GigabitEthernet1/0/5] quit

# Enable SR-MPLS in OSPF view and configure an OSPF prefix SID.

[PE2] ospf 1

[PE2-ospf-1] segment-routing mpls

[PE2-ospf-1] quit

[PE2] interface loopback 1

[PE2-LoopBack1] ospf 1 prefix-sid index 50

[PE2-LoopBack1] quit

# Create VPN instance vpn1, and configure the RD and route target attributes.

[PE2] ip vpn-instance vpn1

[PE2-vpn-instance-vpn1] route-distinguisher 11:11

[PE2-vpn-instance-vpn1] vpn-target 1:1 2:2 3:3 import-extcommunity

[PE2-vpn-instance-vpn1] vpn-target 3:3 export-extcommunity

[PE2-vpn-instance-vpn1] quit

# Associate GigabitEthernet 1/0/1 with VPN instance vpn1, and assign an IP address to the interface.

[PE2] interface gigabitethernet 1/0/1

[PE2-GigabitEthernet1/0/1] ip binding vpn-instance vpn1

[PE2-GigabitEthernet1/0/1] ip address 20.0.0.1 24

[PE2-GigabitEthernet1/0/1] quit

# Create a routing policy and specify a label index value.

[PE2] route-policy policy1 permit node 1

[PE2-route-policy-policy1-1] apply label-index 50

[PE2-route-policy-policy1-1] quit

# Start BGP on PE 2. Enable the capability to exchange labeled routes with IBGP peer 4.4.4.9.

[PE2] bgp 600

[PE2-bgp-default] peer 4.4.4.9 as-number 600

[PE2-bgp-default] peer 4.4.4.9 connect-interface loopback 1

[PE2-bgp-default] address-family ipv4 unicast

[PE2-bgp-default-ipv4] peer 4.4.4.9 enable

[PE2-bgp-default-ipv4] peer 4.4.4.9 label-route-capability

# Enable SR-MPLS.

[PE2-bgp-default-ipv4] segment-routing mpls

# Redistribute the route of loopback interface 1 to BGP and apply the routing policy.

[PE2-bgp-default-ipv4] network 5.5.5.9 32 route-policy policy1

[PE2-bgp-default-ipv4] quit

# Configure the maximum number of hops from PE 2 to EBGP peer 2.2.2.9 as 10.

[PE2-bgp-default] peer 2.2.2.9 as-number 100

[PE2-bgp-default] peer 2.2.2.9 connect-interface loopback 1

[PE2-bgp-default] peer 2.2.2.9 ebgp-max-hop 10

# Configure peer 2.2.2.9 as a VPNv4 peer.

[PE2-bgp-default] address-family vpnv4

[PE2-bgp-default-vpnv4] peer 2.2.2.9 enable

[PE2-bgp-default-vpnv4] quit

# Configure CE 2 as an EBGP peer of PE 2 and install the learned BGP routes in the routing table of the VPN instance.

[PE2-bgp-default] ip vpn-instance vpn1

[PE2-bgp-default-vpn1] peer 20.0.0.2 as-number 65001

[PE2-bgp-default-vpn1] address-family ipv4 unicast

[PE2-bgp-default-ipv4-vpn1] peer 20.0.0.2 enable

7. Configure CE 2:

# Assign an IP address to interface GigabitEthernet 1/0/1.

<CE2> system-view

[CE2] interface gigabitethernet 1/0/1

[CE2-GigabitEthernet1/0/1] ip address 20.0.0.2 24

[CE2-GigabitEthernet1/0/1] quit

# Establish an EBGP peer relationship with PE 2, and redistribute VPN routes.

[CE2] bgp 65002

[CE2-bgp-default] peer 20.0.0.1 as-number 600

[CE2-bgp-default] address-family ipv4 unicast

[CE2-bgp-default-ipv4] peer 20.0.0.1 enable

[CE2-bgp-default-ipv4] import-route direct

[CE2-bgp-default-ipv4] quit

[CE2-bgp-default] quit

Verifying the configuration

# Execute the display ip routing-table command on CE 1 and CE 2 to verify that they have a route to each other. (Details not shown.)

# Verify that CE 1 and CE 2 can ping each other. (Details not shown.)

# Display MPLS LSP information on PE1.

[PE1] display mpls lsp

FEC Proto In/Out Label Out Inter/NHLFE/LSINDEX

2.2.2.9/32 BGP 3/- -

5.5.5.9/32 BGP -/16050 NHLFE1

5.5.5.9 BGP -/- GE1/0/5

1.1.1.1 Local -/- GE1/0/5

2.2.2.9/32 OSPF 16020/- -

3.3.3.9/32 OSPF 16030/3 GE1/0/5

3.3.3.9/32 OSPF -/3 GE1/0/5

Example: Configuring SR-MPLS to LDP (IS-IS)

Network configuration

As shown in Figure 23, complete the following tasks so Router A and Router C can communicate with each other:

· Configure Router A, Router B, and Router C to run IS-IS.

· Configure Router A and Router B to run SR-MPLS and establish an SRLSP between Router A and Router B.

· Configure Router B and Router C to run LDP to establish a dynamic LSP between Router B and Router C.

· Configure Router B as the SRMS, map the prefix address of the LDP network to an SID, and advertise the mapping to Router A.

Figure 23 Network diagram

‌

Table 5 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Router A	Loop1	1.1.1.1/32	Router B	Loop1	2.2.2.2/32
	GE1/0/1	10.0.0.1/24		GE1/0/1	10.0.0.2/24
Router C	Loop1	3.3.3.3/32		GE1/0/2	11.0.0.1/24
	GE1/0/1	11.0.0.2/24

‌

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure IS-IS on the routers to achieve network level connectivity and set the IS-IS cost style to wide:

# Configure Router A.

<RouterA> system-view

[RouterA] isis 1

[RouterA-isis-1] network-entity 00.0000.0000.0001.00

[RouterA-isis-1] cost-style wide

[RouterA-isis-1] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] isis enable 1

[RouterA-GigabitEthernet1/0/1] quit

[RouterA] interface loopback 1

[RouterA-LoopBack1] isis enable 1

[RouterA-LoopBack1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] network-entity 00.0000.0000.0002.00

[RouterB-isis-1] cost-style wide

[RouterB-isis-1] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] isis enable 1

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] isis enable 1

[RouterB-GigabitEthernet1/0/2] quit

[RouterB] interface loopback 1

[RouterB-LoopBack1] isis enable 1

[RouterB-LoopBack1] quit

# Configure Router C.

<RouterC> system-view

[RouterC] isis 1

[RouterC-isis-1] network-entity 00.0000.0000.0003.00

[RouterC-isis-1] cost-style wide

[RouterC-isis-1] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] isis enable 1

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface loopback 1

[RouterC-LoopBack1] isis enable 1

[RouterC-LoopBack1] quit

3. Configure LSR IDs on the routers:

# Configure Router A.

[RouterA] mpls lsr-id 1.1.1.1

# Configure Router B.

[RouterB] mpls lsr-id 2.2.2.2

# Configure Router C.

[RouterC] mpls lsr-id 3.3.3.3

4. Configure LDP on Router B and Router C:

# Configure Router B.

[RouterB] mpls ldp

[RouterB-ldp] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] mpls enable

[RouterB-GigabitEthernet1/0/2] mpls ldp enable

[RouterB-GigabitEthernet1/0/2] quit

# Configure Router C.

[RouterC] mpls ldp

[RouterC-ldp] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] mpls enable

[RouterC-GigabitEthernet1/0/1] mpls ldp enable

[RouterC-GigabitEthernet1/0/1] quit

5. Enable SR-MPLS on Router A and Router B:

# Configure Router A.

[RouterA] isis 1

[RouterA-isis-1] address-family ipv4

[RouterA-isis-1-ipv4] segment-routing mpls

[RouterA-isis-1-ipv4] quit

[RouterA-isis-1] quit

# Configure Router B.

[RouterB] isis 1

[RouterB-isis-1] address-family ipv4

[RouterB-isis-1-ipv4] segment-routing mpls

[RouterB-isis-1-ipv4] quit

[RouterB-isis-1] quit

6. Configure the SRMS:

# On Router B, configure the IGP to advertise locally configured prefix-SID mappings.

[RouterB] isis 1

[RouterB-isis-1] address-family ipv4

[RouterB-isis-1-ipv4] segment-routing mapping-server advertise-local

[RouterB-isis-1-ipv4] quit

[RouterB-isis-1] quit

# On Router B, configure a prefix-SID mapping.

[RouterB] segment-routing

[RouterB-segment-routing] mapping-server prefix-sid-map 3.3.3.3 32 100

[RouterB-segment-routing] quit

Verifying the configuration

# Display IS-IS SRLSP information on Router A.

[RouterA] display mpls lsp protocol isis

FEC Proto In/Out Label Out Inter/NHLFE/LSINDEX

3.3.3.3/32 ISIS 16100/16100 GE1/0/1

3.3.3.3/32 ISIS -/16100 GE1/0/1

The output shows that the outgoing label of the IS-IS SRLSP entry for Router C is using the SID assigned to Router C.

Example: Configuring SR-MPLS to LDP (OSPF)

Network configuration

As shown in Figure 24, complete the following tasks so Router A and Router C can communicate with each other:

· Configure Router A, Router B, and Router C to run OSPF.

· Configure Router A and Router B to run SR-MPLS and establish an SRLSP between Router A and Router B.

· Configure Router B and Router C to run LDP to establish a dynamic LSP between Router B and Router C.

· Configure Router B as the SRMS, map the prefix address of the LDP network to an SID, and advertise the mapping to Router A.

Figure 24 Network diagram

‌

Table 6 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Router A	Loop1	1.1.1.1/32	Router B	Loop1	2.2.2.2/32
	GE1/0/1	10.0.0.1/24		GE1/0/1	10.0.0.2/24
Router C	Loop1	3.3.3.3/32		GE1/0/2	11.0.0.1/24
	GE1/0/1	11.0.0.2/24

‌

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure OSPF on the routers to achieve network level connectivity:

# Configure Router A.

<RouterA> system-view

[RouterA] ospf 1 router-id 1.1.1.1

[RouterA-ospf-1] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] ospf 1 area 0

[RouterA-GigabitEthernet1/0/1] quit

[RouterA] interface loopback 1

[RouterA-LoopBack1] ospf 1 area 0

[RouterA-LoopBack1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] ospf 1 router-id 2.2.2.2

[RouterB-ospf-1] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] ospf 1 area 0

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] ospf 1 area 0

[RouterB-GigabitEthernet1/0/2] quit

[RouterB] interface loopback 1

[RouterB-LoopBack1] ospf 1 area 0

[RouterB-LoopBack1] quit

# Configure Router C.

<RouterC> system-view

[RouterC] ospf 1 router-id 3.3.3.3

[RouterC-ospf-1] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] ospf 1 area 0

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface loopback 1

[RouterC-LoopBack1] ospf 1 area 0

[RouterC-LoopBack1] quit

3. Configure LSR IDs on the routers:

# Configure Router A.

[RouterA] mpls lsr-id 1.1.1.1

# Configure Router B.

[RouterB] mpls lsr-id 2.2.2.2

# Configure Router C.

[RouterC] mpls lsr-id 3.3.3.3

4. Configure LDP on Router B and Router C:

# Configure Router B.

[RouterB] mpls ldp

[RouterB-ldp] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] mpls enable

[RouterB-GigabitEthernet1/0/2] mpls ldp enable

[RouterB-GigabitEthernet1/0/2] quit

# Configure Router C.

[RouterC] mpls ldp

[RouterC-ldp] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] mpls enable

[RouterC-GigabitEthernet1/0/1] mpls ldp enable

[RouterC-GigabitEthernet1/0/1] quit

5. Enable SR-MPLS on Router A and Router B:

# Configure Router A.

[RouterA] ospf 1

[RouterA-ospf-1] segment-routing mpls

[RouterA-ospf-1] quit

# Configure Router B.

[RouterB] ospf 1

[RouterB-ospf-1] segment-routing mpls

[RouterB-ospf-1] quit

6. Configure the SRMS:

# On Router B, configure the IGP to advertise locally configured prefix-SID mappings.

[RouterB] ospf 1

[RouterB-ospf-1] segment-routing mapping-server advertise-local

[RouterB-ospf-1] quit

# On Router B, configure a prefix-SID mapping.

[RouterB] segment-routing

[RouterB-segment-routing] mapping-server prefix-sid-map 3.3.3.3 32 100

[RouterB-segment-routing] quit

Verifying the configuration

# Display OSPF SRLSP information on Router A.

[RouterA] display mpls lsp protocol ospf

FEC Proto In/Out Label Out Inter/NHLFE/LSINDEX

3.3.3.3/32 OSPF 16100/16100 GE1/0/1

3.3.3.3/32 OSPF -/16100 GE1/0/1

The output shows that the outgoing label of the OSPF SRLSP entry for Router C is using the SID assigned to Router C.

Example: Configuring SR-MPLS over LDP

Network configuration

As shown in Figure 25, complete the following tasks so the two SR networks can communicate across the LDP network:

· Configure Router A, Router B, Router C, Router D, and Router E to run IS-IS.

· Configure Router B, Router C, and Router D to run LDP.

· Configure Router A, Router B, Router D, and Router E to run SR-MPLS.

Figure 25 Network diagram

‌

Table 7 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Router A	Loop1	1.1.1.1/32	Router B	Loop1	2.2.2.2/32
	GE1/0/1	10.0.0.1/24		GE1/0/1	10.0.0.2/24
Router C	Loop1	3.3.3.3/32		GE1/0/2	11.0.0.1/24
	GE1/0/1	11.0.0.2/24	Router D	Loop1	4.4.4.4/32
	GE1/0/2	12.0.0.1/24		GE1/0/1	12.0.0.2/24
Router E	Loop1	5.5.5.5/32		GE1/0/2	13.0.0.1/24
	GE1/0/1	13.0.0.2/24

‌

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure IS-IS on the routers to achieve network level connectivity and set the IS-IS cost style to wide:

# Configure Router A.

<RouterA> system-view

[RouterA] isis 1

[RouterA-isis-1] network-entity 00.0000.0000.0001.00

[RouterA-isis-1] cost-style wide

[RouterA-isis-1] quit

[RouterA] interface gigabitethernet 1/0/1

[RouterA-GigabitEthernet1/0/1] isis enable 1

[RouterA-GigabitEthernet1/0/1] quit

[RouterA] interface loopback 1

[RouterA-LoopBack1] isis enable 1

[RouterA-LoopBack1] quit

# Configure Router B.

<RouterB> system-view

[RouterB] isis 1

[RouterB-isis-1] network-entity 00.0000.0000.0002.00

[RouterB-isis-1] cost-style wide

[RouterB-isis-1] quit

[RouterB] interface gigabitethernet 1/0/1

[RouterB-GigabitEthernet1/0/1] isis enable 1

[RouterB-GigabitEthernet1/0/1] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] isis enable 1

[RouterB-GigabitEthernet1/0/2] quit

[RouterB] interface loopback 1

[RouterB-LoopBack1] isis enable 1

[RouterB-LoopBack1] quit

# Configure Router C.

<RouterC> system-view

[RouterC] isis 1

[RouterC-isis-1] network-entity 00.0000.0000.0003.00

[RouterC-isis-1] cost-style wide

[RouterC-isis-1] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] isis enable 1

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface gigabitethernet 1/0/2

[RouterC-GigabitEthernet1/0/2] isis enable 1

[RouterC-GigabitEthernet1/0/2] quit

[RouterC] interface loopback 1

[RouterC-LoopBack1] isis enable 1

[RouterC-LoopBack1] quit

# Configure Router D.

<RouterD> system-view

[RouterD] isis 1

[RouterD-isis-1] network-entity 00.0000.0000.0004.00

[RouterD-isis-1] cost-style wide

[RouterD-isis-1] quit

[RouterD] interface gigabitethernet 1/0/1

[RouterD-GigabitEthernet1/0/1] isis enable 1

[RouterD-GigabitEthernet1/0/1] quit

[RouterD] interface gigabitethernet 1/0/2

[RouterD-GigabitEthernet1/0/2] isis enable 1

[RouterD-GigabitEthernet1/0/2] quit

[RouterD] interface loopback 1

[RouterD-LoopBack1] isis enable 1

[RouterD-LoopBack1] quit

# Configure Router E.

<RouterE> system-view

[RouterE] isis 1

[RouterE-isis-1] network-entity 00.0000.0000.0005.00

[RouterE-isis-1] cost-style wide

[RouterE-isis-1] quit

[RouterE] interface gigabitethernet 1/0/1

[RouterE-GigabitEthernet1/0/1] isis enable 1

[RouterE-GigabitEthernet1/0/1] quit

[RouterE] interface loopback 1

[RouterE-LoopBack1] isis enable 1

[RouterE-LoopBack1] quit

3. Configure LSR IDs on the routers:

# Configure Router A.

[RouterA] mpls lsr-id 1.1.1.1

# Configure Router B.

[RouterB] mpls lsr-id 2.2.2.2

# Configure Router C.

[RouterC] mpls lsr-id 3.3.3.3

# Configure Router D.

[RouterD] mpls lsr-id 4.4.4.4

# Configure Router E.

[RouterE] mpls lsr-id 5.5.5.5

4. Configure LDP on Router B, Router C, and Router D:

# Configure Router B.

[RouterB] mpls ldp

[RouterB-ldp] quit

[RouterB] interface gigabitethernet 1/0/2

[RouterB-GigabitEthernet1/0/2] mpls enable

[RouterB-GigabitEthernet1/0/2] mpls ldp enable

[RouterB-GigabitEthernet1/0/2] quit

# Configure Router C.

[RouterC] mpls ldp

[RouterC-ldp] quit

[RouterC] interface gigabitethernet 1/0/1

[RouterC-GigabitEthernet1/0/1] mpls enable

[RouterC-GigabitEthernet1/0/1] mpls ldp enable

[RouterC-GigabitEthernet1/0/1] quit

[RouterC] interface GigabitEthernet1/0/2

[RouterC-GigabitEthernet1/0/2] mpls enable

[RouterC-GigabitEthernet1/0/2] mpls ldp enable

[RouterC-GigabitEthernet1/0/2] quit

# Configure Router D.

[RouterD] mpls ldp

[RouterD-ldp] quit

[RouterD] interface gigabitethernet 1/0/1

[RouterD-GigabitEthernet1/0/1] mpls enable

[RouterD-GigabitEthernet1/0/1] mpls ldp enable

[RouterD-GigabitEthernet1/0/1] quit

5. Enable SR-MPLS on Router A, Router B, Router D, and Router E:

# Configure Router A.

[RouterA] isis 1

[RouterA-isis-1] address-family ipv4

[RouterA-isis-1-ipv4] segment-routing mpls

[RouterA-isis-1-ipv4] quit

[RouterA-isis-1] quit

# Configure Router B.

[RouterB] isis 1

[RouterB-isis-1] address-family ipv4

[RouterB-isis-1-ipv4] segment-routing mpls

[RouterB-isis-1-ipv4] quit

[RouterB-isis-1] quit

# Configure Router D.

[RouterD] isis 1

[RouterD-isis-1] address-family ipv4

[RouterD-isis-1-ipv4] segment-routing mpls

[RouterD-isis-1-ipv4] quit

[RouterD-isis-1] quit

# Configure Router E.

[RouterE] isis 1

[RouterE-isis-1] address-family ipv4

[RouterE-isis-1-ipv4] segment-routing mpls

[RouterE-isis-1-ipv4] quit

[RouterE-isis-1] quit

6. Configure IS-IS prefix SIDs for Router A, Router B, Router D, and Router E:

# Configure Router A.

[RouterA] interface loopback 1

[RouterA-LoopBack1] isis prefix-sid index 10

[RouterA-LoopBack1] quit

# Configure Router B.

[RouterB] interface loopback 1

[RouterB-LoopBack1] isis prefix-sid index 20

[RouterB-LoopBack1] quit

# Configure Router D.

[RouterD] interface loopback 1

[RouterD-LoopBack1] isis prefix-sid index 40

[RouterD-LoopBack1] quit

# Configure Router E.

[RouterE] interface loopback 1

[RouterE-LoopBack1] isis prefix-sid index 50

[RouterE-LoopBack1] quit

Verifying the configuration

# Display LDP LSP information on Router B.

[RouterB] display mpls ldp lsp

Status Flags: * - stale, L - liberal, B - backup, N/A - unavailable

FECs: 5 Ingress: 3 Transit: 3 Egress: 2

FEC In/Out Label Nexthop OutInterface

1.1.1.1/32 2173/-

-/2173(L)

2.2.2.2/32 3/-

-/2175(L)

3.3.3.3/32 -/3 11.0.0.2 GE1/0/2

2175/3 11.0.0.2 GE1/0/2

4.4.4.4/32 -/2174 11.0.0.2 GE1/0/2

2174/2174 11.0.0.2 GE1/0/2

5.5.5.5/32 -/2172 11.0.0.2 GE1/0/2

2172/2172 11.0.0.2 GE1/0/2

# Display IS-IS SRLSP information on Router B.

[RouterB] display mpls lsp protocol isis

FEC Proto In/Out Label Interface/Out NHLFE

1.1.1.1/32 ISIS 16010/3 GE1/0/1

1.1.1.1/32 ISIS -/3 GE1/0/1

2.2.2.2/32 ISIS 16020/- -

4.4.4.4/32 ISIS 16040/2174 GE1/0/2

4.4.4.4/32 ISIS -/2174 GE1/0/2

5.5.5.5/32 ISIS 16050/2172 GE1/0/2

5.5.5.5/32 ISIS -/2172 GE1/0/2

The output shows that the IS-IS SRLSP entries for Router D and Router E are using LDP outgoing labels.

Example: Configuring IS-IS TI-LFA FRR

Network configuration

As shown in Figure 26, complete the following tasks to implement TI-LFA FRR:

· Configure IS-IS on Device A, Device B, and Device C to achieve network level connectivity.

· Configure SR-MPLS on Device A, Device B, and Device C.

· Configure TI-LFA FRR to remove the loop that exists on Link B and to implement fast traffic switchover to Link B when Link A fails.

Figure 26 Network diagram

‌

Table 8 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Device A	Loop1	1.1.1.1/32	Device B	Loop1	2.2.2.2/32
	GE1/0/1	12.12.12.1/24		GE1/0/1	24.24.24.1/24
	GE1/0/2	13.13.13.1/24		GE1/0/2	13.13.13.2/24
Device C	Loop1	3.3.3.3/32
	GE1/0/1	12.12.12.2/24
	GE1/0/2	24.24.24.2/24

‌

Procedure

1. Configure IP addresses and masks for interfaces. (Details not shown.)

2. Configure IS-IS on the switches to achieve network level connectivity and set the IS-IS cost style to wide:

# Configure Device A.

<DeviceA> system-view

[DeviceA] isis 1

[DeviceA-isis-1] network-entity 00.0000.0000.0001.00

[DeviceA-isis-1] cost-style wide

[DeviceA-isis-1] quit

[DeviceA] interface gigabitethernet 1/0/1

[DeviceA-GigabitEthernet1/0/1] isis enable 1

[DeviceA-GigabitEthernet1/0/1] isis cost 10

[DeviceA-GigabitEthernet1/0/1] quit

[DeviceA] interface gigabitethernet 1/0/2

[DeviceA-GigabitEthernet1/0/2] isis enable 1

[DeviceA-GigabitEthernet1/0/2] isis cost 10

[DeviceA-GigabitEthernet1/0/2] quit

[DeviceA] interface loopback 1

[DeviceA-LoopBack1] isis enable 1

[DeviceA-LoopBack1] quit

# Configure Device B.

<DeviceB> system-view

[DeviceB] isis 1

[DeviceB-isis-1] network-entity 00.0000.0000.0002.00

[DeviceB-isis-1] cost-style wide

[DeviceB-isis-1] quit

[DeviceB] interface gigabitethernet 1/0/1

[DeviceB-GigabitEthernet1/0/1] isis enable 1

[DeviceB-GigabitEthernet1/0/1] isis cost 20

[DeviceB-GigabitEthernet1/0/1] quit

[DeviceB] interface gigabitethernet 1/0/2

[DeviceB-GigabitEthernet1/0/2] isis enable 1

[DeviceB-GigabitEthernet1/0/2] isis cost 10

[DeviceB-GigabitEthernet1/0/2] quit

[DeviceB] interface loopback 1

[DeviceB-LoopBack1] isis enable 1

[DeviceB-LoopBack1] quit

# Configure Device C.

<DeviceC> system-view

[DeviceC] isis 1

[DeviceC-isis-1] network-entity 00.0000.0000.0003.00

[DeviceC-isis-1] cost-style wide

[DeviceC-isis-1] quit

[DeviceC] interface gigabitethernet 1/0/1

[DeviceC-GigabitEthernet1/0/1] isis enable 1

[DeviceC-GigabitEthernet1/0/1] isis cost 10

[DeviceC-GigabitEthernet1/0/1] quit

[DeviceC] interface gigabitethernet 1/0/2

[DeviceC-GigabitEthernet1/0/2] isis enable 1

[DeviceC-GigabitEthernet1/0/2] isis cost 20

[DeviceC-GigabitEthernet1/0/2] quit

[DeviceC] interface loopback 1

[DeviceC-LoopBack1] isis enable 1

[DeviceC-LoopBack1] quit

3. Configure MPLS TE settings:

# Configure Device A.

[DeviceA] mpls lsr-id 1.1.1.1

[DeviceA] mpls te

[DeviceA-te] quit

[DeviceA] interface gigabitethernet 1/0/1

[DeviceA-GigabitEthernet1/0/1] mpls enable

[DeviceA-GigabitEthernet1/0/1] mpls te enable

[DeviceA-GigabitEthernet1/0/1] quit

[DeviceA] interface gigabitethernet 1/0/2

[DeviceA-GigabitEthernet1/0/2] mpls enable

[DeviceA-GigabitEthernet1/0/2] mpls te enable

[DeviceA-GigabitEthernet1/0/2] quit

# Configure Device B.

[DeviceB] mpls lsr-id 2.2.2.2

[DeviceB] mpls te

[DeviceB-te] quit

[DeviceB] interface gigabitethernet 1/0/1

[DeviceB-GigabitEthernet1/0/1] mpls enable

[DeviceB-GigabitEthernet1/0/1] mpls te enable

[DeviceB-GigabitEthernet1/0/1] quit

[DeviceB] interface gigabitethernet 1/0/2

[DeviceB-GigabitEthernet1/0/2] mpls enable

[DeviceB-GigabitEthernet1/0/2] mpls te enable

[DeviceB-GigabitEthernet1/0/2] quit

# Configure Device C.

[DeviceC] mpls lsr-id 3.3.3.3

[DeviceC] mpls te

[DeviceC-te] quit

[DeviceC] interface gigabitethernet 1/0/1

[DeviceC-GigabitEthernet1/0/1] mpls enable

[DeviceC-GigabitEthernet1/0/1] mpls te enable

[DeviceC-GigabitEthernet1/0/1] quit

[DeviceC] interface gigabitethernet 1/0/2

[DeviceC-GigabitEthernet1/0/2] mpls enable

[DeviceC-GigabitEthernet1/0/2] mpls te enable

[DeviceC-GigabitEthernet1/0/2] quit

4. Enable SR-MPLS and SR-MPLS adjacency label allocation:

# Configure Device A.

[DeviceA] isis 1

[DeviceA-isis-1] address-family ipv4

[DeviceA-isis-1-ipv4] segment-routing mpls

[DeviceA-isis-1-ipv4] segment-routing adjacency enable

[DeviceA-isis-1-ipv4] quit

[DeviceA-isis-1] quit

# Configure Device B.

[DeviceB] isis 1

[DeviceB-isis-1] address-family ipv4

[DeviceB-isis-1-ipv4] segment-routing mpls

[DeviceB-isis-1-ipv4] segment-routing adjacency enable

[DeviceB-isis-1-ipv4] quit

[DeviceB-isis-1] quit

# Configure Device C.

[DeviceC] isis 1

[DeviceC-isis-1] address-family ipv4

[DeviceC-isis-1-ipv4] segment-routing mpls

[DeviceC-isis-1-ipv4] segment-routing adjacency enable

[DeviceC-isis-1-ipv4] quit

[DeviceC-isis-1] quit

5. Configure IS-IS prefix SIDs for Device A, Device B, and Device C:

# Configure Device A.

[DeviceA] interface loopback 1

[DeviceA-LoopBack1] isis prefix-sid index 10

[DeviceA-LoopBack1] quit

# Configure Device B.

[DeviceB] interface loopback 1

[DeviceB-LoopBack1] isis prefix-sid index 20

[DeviceB-LoopBack1] quit

# Configure Device C.

[DeviceC] interface loopback 1

[DeviceC-LoopBack1] isis prefix-sid index 30

[DeviceC-LoopBack1] quit

6. Configure TI-LFA FRR:

# Configure Device A.

[DeviceA] isis 1

[DeviceA-isis-1] address-family ipv4

[DeviceA-isis-1-ipv4] fast-reroute lfa

[DeviceA-isis-1-ipv4] fast-reroute ti-lfa

[DeviceA-isis-1-ipv4] fast-reroute microloop-avoidance enable

[DeviceA-isis-1-ipv4] segment-routing microloop-avoidance enable

[DeviceA-isis-1-ipv4] quit

[DeviceA-isis-1] quit

# Configure Device B.

[DeviceB] isis 1

[DeviceB-isis-1] address-family ipv4

[DeviceB-isis-1-ipv4] fast-reroute lfa

[DeviceB-isis-1-ipv4] fast-reroute ti-lfa

[DeviceB-isis-1-ipv4] fast-reroute microloop-avoidance enable

[DeviceB-isis-1-ipv4] segment-routing microloop-avoidance enable

[DeviceB-isis-1-ipv4] quit

[DeviceB-isis-1] quit

# Configure Device C.

[DeviceC] isis 1

[DeviceC-isis-1] address-family ipv4

[DeviceC-isis-1-ipv4] fast-reroute lfa

[DeviceC-isis-1-ipv4] fast-reroute ti-lfa

[DeviceC-isis-1-ipv4] fast-reroute microloop-avoidance enable

[DeviceC-isis-1-ipv4] segment-routing microloop-avoidance enable

[DeviceC-isis-1-ipv4] quit

[DeviceC-isis-1] quit

Verifying the configuration

# Display IPv4 IS-IS routing information for 2.2.2.2/32.

[DeviceA] display isis route ipv4 2.2.2.2 32 verbose level-1 1

Route information for IS-IS(1)

-----------------------------

Level-1 IPv4 Forwarding Table

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IPv4 Dest : 2.2.2.2/32 Int. Cost : 10 Ext. Cost : NULL

Admin Tag : - Src Count : 1 Flag : R/L/-

InLabel : 16020 InLabel Flag: -/N/-/-/-/-

NextHop : Interface : ExitIndex :

13.13.13.2 GE1/0/2 0x00000103

Nib ID : 0x14000005 OutLabel : 16020 OutLabelFlag: I

LabelSrc : SR

TI-LFA:

Interface : GE1/0/1

BkNextHop : 12.12.12.2 LsIndex : 0x00000002

Backup label stack(top->bottom): {16030, 2175}

Route label: 16020

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

InLabel flags: R-Readvertisement, N-Node SID, P-no PHP

E-Explicit null, V-Value, L-Local

OutLabelFlags: E-Explicit null, I-Implicit null, N-Nomal, P-SR label prefer

The output shows TI-LFA backup next hop information.

23-Segment Routing Configuration Guide

Static segment configuration

Prefix SID

Adjacency SID

Label forwarding entry installation based on IGP prefix SIDs

Label forwarding entry installation based on BGP prefix SIDs

Label forwarding entry installation based on BGP EPE

Label forwarding entry installation based on adjacency SIDs

SRLSP setup

Prefix SID-based packet forwarding across ASs

BGP EPE-based packet forwarding across ASs

Adjacency SID-based packet forwarding

Prefix and adjacency SID-based packet forwarding

TI-LFA FRR advantages

TI-LFA FRR concepts

TI-LFA FRR protection types

Restrictions and guidelines

Configuring the global MPLS SRGB

Configuring the MPLS SRGB for IS-IS

Configuring the MPLS SRGB for OSPF

About this task

Restrictions and guidelines

Procedure

Restrictions and guidelines

Procedure

Restrictions and guidelines

Procedure

Configuring IGP-based SID advertisement

GP-based prefix SID advertisement tasks at a glance

IGP-based adjacency SID advertisement tasks at a glance

Prerequisites

Configuring IS-IS to support SR-MPLS

Configuring OSPF to support SR-MPLS

About this task

Restrictions and guidelines

Configuring an IS-IS prefix SID

Configuring an OSPF prefix SID

Enabling SR-MPLS adjacency label allocation for the IGP

Restrictions and guidelines

Enabling SR-MPLS adjacency label allocation for IS-IS

Enabling SR-MPLS adjacency label allocation for OSPF

About this task

Restrictions and guidelines

Prerequisites

Assigning adjacency SIDs to IS-IS adjacencies

Assigning adjacency SIDs to OSPF adjacencies

About this task

Restrictions and guidelines

Configuring the device to use the SIDs advertised by the IGP

Specifying a routing policy for route redistribution

Restrictions and guidelines

Procedure

About this task

Restrictions and guidelines

Prerequisites

Procedure

About this task

Restrictions and guidelines

Configuring the device to prefer SRLSPs established by IS-IS in traffic forwarding

Configuring the device to prefer SRLSPs established by OSPF in traffic forwarding

SRMS tasks at a glance

SRMC tasks at a glance

Enabling advertisement of locally configured prefix-SID mappings

Restrictions and guidelines

Configuring IS-IS to advertise locally configured prefix-SID mappings

Configuring OSPF to advertise locally configured prefix-SID mappings

Configuring prefix-SID mappings

Restrictions and guidelines

Prerequisites

Procedure

Restrictions and guidelines

Configuring IS-IS to receive advertised prefix-SID mappings

Configuring OSPF to receive advertised prefix-SID mappings

Restrictions and guidelines

Procedure