Segment Routing (SR) is a source routing technology. The source node selects a path for packet forwarding, 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.

IPv6 Segment Routing (SRv6) uses IPv6 addresses as SIDs to forward packets.

Basic concepts

SR node

An SR node is a node that supports the SRv6 feature. The following SR nodes are available:

· Ingress node (source node)—Selects a path for packet forwarding, encodes the path as an ordered SID list in the routing extension header.

· Transit node—Forwards the packets based on the SID list.

· Egress node (tail node)—Removes the routing extension header and forwards the packets to the destination.

SID

SRv6 supports SRv6 SIDs that have specific functions.

An SRv6 SID is in the format of IPv6 address, but the IPv6 address does not belong to any interface on any device.

As shown in Figure 1, an SRv6 SID contains the Locator, Function, Arguments, and Must be zero (MBZ) portions.

· Locator—Identifies the network segment of the SID. The locator of an SRv6 SID must be unique in the SR domain.

· Function—Contains an opcode that identifies the network function of an SID. An SR node will execute the function in the SRv6 SID Function field of an SRv6 packet after it receives that SRv6 packet.

· Arguments—Defines flow and service parameters for SRv6 packets.

· MBZ—When the total number of bits in the Locator, Function, and Arguments portions is less than 128 bits, the remaining bits are padded with 0s.

Figure 1 SRv6 SID

‌

According to whether SRv6 SIDs are compressible, SRv6 SIDs are non compressible.

Non-compressible SRv6 SIDs include static and dynamic SRv6 SIDs. The formats are as follows:

· A static SRv6 SID is generated based on the following formula: static SRv6 SID = ipv6-prefix + 0 + opcode + 0.

¡ The ipv6-prefix portion represents the IPv6 prefix specified by using the ipv6-address and prefix-length arguments in the locator command. The number of bits occupied by the IPv6 prefix is configured by using the prefix-length argument.

¡ The number of bits occupied by 0s (following the ipv6-prefix portion) is 128 - prefix-length - static-length - args-length.

¡ opcode represents the static portion in the Function field. The number of bits occupied by the opcode is the value of the static-length argument. The number of bits occupied by 0s (following the opcode portion) is the value of the args-length argument.

· A dynamic SRv6 SID is generated based on the following formula: dynamic SRv6 SID = ipv6-prefix + dynamic + static + 0.

¡ dynamic represents the dynamic portion in the Function field. The value for this portion cannot be all zeros. The number of bits occupied by this portion is 128 - prefix-length - static-length - args-length.

¡ static represents the static portion in the Function field. The number of bits occupied by this portion is static-length. This portion can use any value. The number of bits occupied by 0s is the value of the args-length argument.

For example, use the locator test1 ipv6-prefix 100:200:DB8:ABCD:: 64 static 24 args 32 command.

· The locator is 100:200:DB8:ABCD::. The prefix length is 64 bits.

· The static portion length is 24 bits.

· The Args portion length is 32 bits.

· The dynamic portion length is 8 bits.

In this example, the following non-compressible static SRv6 SID range and dynamic SRv6 SID range are obtained on the locator:

· The start value for static SRv6 SIDs is 100:200:DB8:ABCD:0:1::.

· The end value for static SRv6 SIDs is 100:200:DB8:ABCD:FF:FFFF::.

· The start value for dynamic SRv6 SIDs is 100:200:DB8:ABCD:100::.

· The end value for dynamic SRv6 SIDs is 100:200:DB8:ABCD:FFFF:FFFF::.

Figure 2 Non-compressible SRv6 SIDs

According to the functions of SRv6 SIDs, SRv6 SIDs are divided into the following categories:

· End SID—Identifies the prefix of a destination address in the network.

· End.X SID—Identifies a link in the network.

· End.DT4 SID—Identifies an IPv4 VPN in the network. The function of an End.DT4 SID is decapsulating packets and searching the routing table of the corresponding IPv4 VPN instance to forward the packets. End.DT4 SIDs are applicable to IP L3VPN and EVPN L3VPN scenarios.

· End.DT6 SID—Identifies an IPv6 VPN in the network. The function of an End.DT6 SID is decapsulating packets and searching the routing table of the corresponding IPv6 VPN instance to forward the packets. End.DT6 SIDs are applicable to IPv6 L3VPN and IPv6 EVPN L3VPN scenarios.

· End.DT46 SID—Identifies an IPv4 or IPv6 VPN in the network.

· End.DX2 SID—Identifies one end of a Layer 2 cross-connect. The function of an End.DX2 SID is removing the outer IPv6 header and SRH of packets and forwarding the decapsulated packets to the output interface of the SID. End.DX2 SIDs are applicable to EVPN VPWS scenarios.

· End.DX2L SID—Identifies packets that come from a bypass SRv6 PW. The packets will not be forwarded back to the bypass SRv6 PW for loop prevention. The function of an End.DX2L SID is removing the outer IPv6 header and SRH of packets and forwarding the decapsulated packets to the output interface of the SID. End.DX2L SIDs are applicable to EVPN VPWS over SRv6 multihomed sites.

· End.DT2M SID—Identifies one end of a Layer 2 cross-connect and floods traffic. The function of an End.DT2M SID is removing the outer IPv6 header and SRH of packets and flooding the decapsulated packets in the VSI. End.DT2M SIDs are applicable to EVPN VPLS BUM traffic.

· End.DT2U SID—Identifies one end of a Layer 2 cross-connect and performs unicast forwarding. The function of an End.DT2U SID is removing the outer IPv6 header and SRH of packets, looking up the MAC address table for the destination MAC address, and forwarding the packets to the output interface based on the MAC address entry. End.DT2U SIDs are applicable to EVPN VPLS unicast traffic.

· End.DT2UL SID—Identifies packets that come from a bypass SRv6 PW. The packets will not be forwarded back to the bypass SRv6 PW for loop prevention. The function of an End.DT2UL SID is removing the outer IPv6 header and SRH of packets and forwarding the packets to the output interface through destination MAC address lookup. End.DT2UL SIDs are applicable to EVPN VPLS over SRv6 multihomed sites.

· End.M SID—Applies to the SRv6 TE policy tailend protection scenario. For more information about End.M SIDs, see "Configuring SRv6 TE policies."

· End.OP SID—Applies to the SRv6 OAM scenario. For more information about End.OP SIDs, see "Configuring SRv6 OAM."

Use IGP to advertise SRv6 SIDs for an SR node. The other SR nodes will generate route entries of that SR node based on the advertised information.

SRv6 SID flavors

Use SRv6 SID flavors to change the forwarding behaviors of SRv6 SIDs in order to meet multiple service requirements. The following SRv6 SID flavors are supported:

· Penultimate Segment POP of the SRH (PSP)—The penultimate SRv6 node removes the SRH to reduce the workload of the end SRv6 node and improve the forwarding efficiency. The end SRv6 node does not read the SRH, and it only looks up the local SID table for the destination IPv6 address of packets to forward the packets.

· NO PSP—The penultimate SRv6 node does not remove the SRH.

Local SID forwarding table

An SRv6-enabled node maintains a local SID forwarding table that records the SRv6 SIDs generated on the local node. The local SID forwarding table has the following functions:

· Stores local generated SRv6 SID forwarding information.

· Stores SRv6 SID operation types.

Segment List

A Segment List is an ordered list of SIDs, which is also referred to as a Segment Identifier (SID) list in this document. The SR nodes forward packets based on the SIDs in the order that they are arranged in the SID list.

SRv6 packet format

An outer IPv6 header and a Segment Routing Header (SRH) are added to the original Layer 3 data packet to form an SRv6 packet.

As shown in Figure 3, the value for the Next Header field is 43 in the outer IPv6 header, which indicates that the header next to the IPv6 header is a routing extension header. The value for the Routing Type field in the routing extension header is 4, which indicates that the routing extension header is an SRH. The SRH header contains the following fields:

· 8-bit Next Header—Identifies the type of the header next to the SRH.

· 8-bit Hdr Ext Len—Length of the SRH header in 8-octet units, not including the first 8 octets.

· 8-bit Routing Type—The value for this field is 4, which represents SRH.

· 8-bit Segments Left—Contains the index of the next segment to inspect in the Segment List. The Segments Left field is set to n-1 where n is the number of segments in the Segment List. Segments Left is decremented at each segment.

· 8-bit Last Entry—Contains the index of the first SID in the path used to forward the packet.

· 8-bit Flags—Contains flags.

· 16-bit Tag—Tags a packet as part of a class or group of packets, for example, packets sharing the same set of properties.

· Segment List—Contains 128-bit IPv6 addresses representing the ordered segments. The Segment List is encoded starting from the last segment of the path. The first element of the segment list (Segment List [0]) contains the last segment of the path, the second element (Segment List [1]) contains the penultimate segment of the path and so on. The number enclosed in a pair of brackets is the index of a segment.

Figure 3 SRv6 packet format

‌

BGP-EPE

IGP for SRv6 cannot advertise SRv6 SIDs across ASs. To advertise SRv6 SIDs across ASs, use BGP Egress Peer Engineering (BGP-EPE).

BGP-EPE can allocate BGP peer SIDs to inter-AS segments.

· If the device has established BGP LS peer relationship with a network controller, it advertises the peer SIDs to the network controller through extended BGP LS messages. Then, the controller orchestrates the IGP SIDs and BGP peer SIDs to realize optimal inter-AS traffic forwarding.

· If the device has not established BGP LS peer relationship with a network controller, it advertises the peer SIDs to a BGP peer through BGP LS messages. When a device that has established BGP LS peer relationship with a network controller receives the peer SIDs, it advertises the peer SIDs to the network controller through BGP LS messages.

BGP-EPE supports automatic peer SID allocation and static peer SID allocation. As shown in Figure 4, BGP-EPE can allocate the following peer SIDs:

· PeerNode SID—Identifies a peer node. BGP-EPE allocates a PeerNode SID to each BGP session. If the device establishes EBGP peer relationship with a peer through a loopback interface, it might have multiple physical links to reach the peer. In this case, the PeerNode SID for this peer is associated with multiple output interfaces. Traffic destined for this peer based on the PeerNode SID will be distributed among these output interfaces.

· PeerAdj SID—Identifies an adjacency link that can reach a peer node. If the device establishes EBGP peer relationship with a peer through a loopback interface, it might have multiple physical links to reach the peer. Each link is allocated a PeerAdj SID. When the device forwards traffic based on a PeerAdj SID, the traffic is forwarded out of the interface that is attached to the link identified by the PeerAdj SID.

· PeerNode-Adj SID—Identifies a peer node and identifies one or multiple adjacency links that can reach a peer node.

· PeerSet SID—Identifies a group of peer nodes in a BGP-EPE SRv6 peer set. A PeerSet SID corresponds to multiple PeerNode SIDs and PeerAdj SIDs. When the device forwards traffic based on a PeerSet SID, it distributes the traffic among multiple peers.

Figure 4 BGP-EPE network diagram

As shown in Figure 4, BGP-EPE allocates peer SIDs as follows:

· ASBR 1 and ASBR 3 have two direct physical links. They establish EBGP peer relationship through loopback interfaces. On ASBR 1, BGP-EPE allocates PeerNode SID 100:AB::1 to ASBR 3 and allocates PeerAdj SIDs 100:AB:1::2 and 100:AB:1::3 to the physical links. When ASBR 1 forwards traffic to ASBR 3 based on the PeerNode SID, the two physical links load share the traffic.

· EBGP peer relationship has been established between ASBR 1 and ASBR 5, between ARBR 2 and ASBR 4, and between ASBR 2 and ASBR 5 through directly connected physical interfaces. On ASBR 1, BGP-EPE allocates PeerNode SID 100:AB::2 to ASBR 5. On ASBR 2, BGP-EPE allocates PeerNode SIDs 100:AB::4 and 100:AB::5 to ASBR 4 and ASBR 5, respectively.

· ASBR 4 and ASBR 5 each has established EBGP peer relationship with ASBR 2. On ASBR 2, peers ASBR 4 and ASBR 5 are added to a peer set. BGP-EPE allocates PeerSet SID 100:AB::3 to the peer set. When ASBR 2 forwards traffic based on the PeerSet SID, the traffic is distributed to both ASBR 4 and ASBR 5 for load sharing.

The SIDs allocated to peers by BGP-EPE are not advertised to the peers. Route types used by the peers do not affect BGP-EPE.

TI-LFA FRR

Topology-Independent Loop-Free Alternate Fast Re-Route (TI-LFA FRR) provides link and node protection for SRv6 tunnels. When a link or node fails, TI-LFA FRR switches the traffic to the backup path to ensure continuous data forwarding.

TI-LFA FRR background

As shown in Figure 5, node A sends data packets to node F. When the link between node B and node E fails, node B forwards the data packets to node C. The cost of the link between node C and node D is 100 (which is greater than the cost of the link between node C and node D) and the routes on node C have not converged. As a result, node C determines that the next hop of the optimal path to reach node F is node B. Then, node C forwards the data packets back to node B, which causes a loop.

Figure 5 TI-LFA application scenario

‌

To resolve this issue, deploy TI-FLA on the SRv6 network. As shown in Figure 6, when the link between node B and node E fails, node B uses the backup path calculated by TI-LFA to forward the data packets along the B->C->D->E path.

Figure 6 TI-LFA forwarding network diagram

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.

· 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 SRv6 SIDs:

¡ SRv6 SIDs of P nodes.

¡ SRv6 SIDs from P nodes to nearest Q nodes.

TI-LFA FRR path calculation

As shown in Figure 7, 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: End.X SID C of the link between P 2 and P 3 and End.X SID D of the link between P 3 and P 4.

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 7 TI-LFA FRR diagram

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 8, P 2 is a P node and P 4 and PE 2 are Q nodes. 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 looks up the IPv6 routing table for the destination IPv6 address of a packet and finds that the next hop is P 2. PE 1 encapsulates the packet according to the repair list.

¡ Adds an SRH header. The SID list is Segment List [0]=D and Segment List [1]=C. The SIDs are arranged from the farthest node to the nearest node.

¡ Adds an outer IPv6 header. The source address is address A on source node PE 1 and the destination address is the address pointed by SL. Because the SL is 1, the destination address is C as pointed by Segment List [1].

2. After P2 receives the packet, it performs the following operations:

a. Checks the SL value in the SRH header and decreases the value by 1.

b. Searches for the address pointed by Segment List [0] and finds that the address is End.X SID D between P 3 and P 4.

c. Replaces the destination address in the outer IPv6 header with End.X SID D.

d. Obtains the output interface and next hop according to End.X SID C and forwards the encapsulated packet to P 3.

3. After P3 receives the packet, it performs the following operations:

a. Checks the SL value in the SRH header and finds that the SL value is 0.

b. Decapsulates the packet.

c. Obtains the output interface and next hop according to End.X SID D and forwards the packet to P 4.

4. After P4 receives the packet, it searches the IP routing table for the destination IP address of the packet and forwards the packet to PE 2.

Figure 8 Data forwarding over the TI-LFA FRR backup path

SR microloop avoidance after a network failure

As shown in Figure 9, 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.

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 9 Diagram for SR microloop avoidance after a network failure

SR microloop avoidance after a failure recovery

As shown in Figure 10, before the link between Device B and Device C recovers, traffic traverses along the backup path. After the link recovers, Device A forwards the traffic to Device B if Device A finishes route convergence before Device B. With route convergence unfinished, 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.

Upon expiration of the microloop avoidance RIB-update-delay timer and completion of route convergence on Device B, Device A does not add path information to packets anymore. It will forward packets to Device C as usual.

Figure 10 Diagram for SR microloop avoidance after a failure recovery

‌

Protocols and standards

· draft-previdi-6man-segment-routing-header

· draft-ietf-6man-segment-routing-header

· draft-filsfils-spring-segment-routing

· draft-filsfils-spring-srv6-network-programming

SRv6 tasks at a glance

To configure SRv6, perform the following tasks:

1. Configuring SRv6 SIDs

2. (Optional.) Managing SRv6 SIDs

¡ Setting the SRv6 SID flavor to NO-PSP

¡ Setting the SRH encapsulation mode to normal encapsulation

3. (Optional.) Configuring dynamic End.X SID deletion delay

4. Specifying a source address for the outer IPv6 header of SRv6-encapsulated packets

5. Using IGP to advertise SRv6 SIDs

6. Configuring BGP for SRv6

¡ Enabling BGP to advertise routes for a locator

¡ Configuring BGP-EPE

7. (Optional.) Configuring advanced SRv6 features

¡ Configuring traffic forwarding statistics collection for local SRv6 SIDs

¡ Configuring TI-LFA FRR

¡ Configuring the SRv6 MTU

¡ Configuring the SRv6 DiffServ mode

Prerequisites for SRv6

Before you configure an SRv6 tunnel, perform the following tasks:

· Determine the ingress node, transit nodes, and egress node of the SRv6 tunnel.

· Plan the IPv6 address of each SR node.

Configuring SRv6 SIDs

Restrictions and guidelines

Each locator must have a unique name.

Do not configure the same IPv6 address prefix and prefix length for different locators. In addition, the IPv6 address prefixes of different locators cannot overlap.

You cannot disable SRv6 or delete a locator in SRv6 view if the locator has dynamic SRv6 SIDs that are being used.

Procedure

1. Enter system view.

system-view

2. Enable SRv6 and enter SRv6 view.

segment-routing ipv6

3. Configure a locator and enter SRv6 locator view.

locator locator-name [ ipv6-prefix ipv6-address prefix-length [ args args-length | static static-length ] * ]

4. (Optional.) Enable anycast for the locator.

anycast enable

By default, anycast is disabled for a locator.

A locator is an anycast locator if the A-bit is set in the Flags field of the Locator TLV in routing protocol packets. An anycast locator is shared by a group of SRv6 nodes.

5. Configure an opcode. Perform one of the following tasks:

¡ Configure an opcode for End SIDs.

opcode { opcode | hex hex-opcode } end

¡ Configure an opcode for End.X SIDs.

opcode { opcode | hex hex-opcode } end-x interface interface-type interface-number nexthop nexthop-ipv6-address [ path-index index-value | weight weight-value ] *

¡ Configure an opcode for End.DT4 SIDs.

opcode { opcode | hex hex-opcode } end-dt4 [ vpn-instance vpn-instance-name [ evpn | l3vpn-evpn ] ]

The specified VPN instance must exist. The same End.DT4 SIDs cannot be configured in different VPN instances.

¡ Configure an opcode for End.DT6 SIDs.

opcode { opcode | hex hex-opcode } end-dt6 [ vpn-instance vpn-instance-name [ evpn | l3vpn-evpn ] ]

The specified VPN instance must exist. The same End.DT6 SIDs cannot be configured in different VPN instances.

¡ Configure an opcode for End.DT46 SIDs.

opcode { opcode | hex hex-opcode } end-dt46 [ vpn-instance vpn-instance-name [ evpn | l3vpn-evpn ] ]

The specified VPN instance must exist. The same End.DT46 SIDs cannot be configured in different VPN instances.

¡ Configure an opcode for End.DX4 SIDs.

opcode { opcode | hex hex-opcode } end-dx4 interface interface-type interface-number nexthop nexthop-ipv4-address [ vpn-instance vpn-instance-name [ evpn ] ]

The specified VPN instance must exist. The same End.DX4 SIDs cannot be configured with different output interfaces or next hops.

¡ Configure an opcode for End.DX6 SIDs.

opcode { opcode | hex hex-opcode } end-dx6 interface interface-type interface-number nexthop nexthop-ipv6-address [ vpn-instance vpn-instance-name [ evpn ] ]

The specified VPN instance must exist. The same End.DX6 SIDs cannot be configured with different output interfaces or next hops.

¡ Configure an opcode for End.DX2 SIDs.

opcode { opcode | hex hex-opcode } end-dx2 xconnect-group group-name connection connection-name

The specified cross-connect group and cross-connect must exist.

opcode { opcode | hex hex-opcode } end-dx2 vsi vsi-name interface interface-type interface-number service-instance instance-id

The specified VSI must exist.

¡ Configure an opcode for End.DX2L SIDs.

opcode { opcode | hex hex-opcode } end-dx2l xconnect-group group-name connection connection-name

The specified cross-connect group and cross-connect must exist.

opcode { opcode | hex hex-opcode } end-dx2l vsi vsi-name interface interface-type interface-number service-instance instance-id

The specified VSI must exist.

¡ Configure an opcode for End.DT2M SIDs.

opcode { opcode | hex hex-opcode } end-dt2m vsi vsi-name

The specified VSI must exist. The same End.DT2M SIDs cannot be configured in different VSIs.

¡ Configure an opcode for End.DT2U SIDs.

opcode { opcode | hex hex-opcode } end-dt2u vsi vsi-name

The specified VSI must exist. The same End.DT2U SIDs cannot be configured in different VSIs.

¡ Configure an opcode for End.DT2UL SIDs.

opcode { opcode | hex hex-opcode } end-dt2ul vsi vsi-name

The specified VSI must exist. The same End.DT2UL SIDs cannot be configured in different VSIs.

¡ Configure an opcode for End.M SIDs.

opcode { opcode | hex hex-opcode } end-m mirror-locator ipv6-address prefix-length

¡ Configure an opcode for End.OP SIDs.

opcode { opcode | hex hex-opcode } end-op

Setting the SRv6 SID flavor to NO-PSP

About this task

Perform this task to set the flavor of SRv6 SIDs in a unified manner to reduce user workload. The following flavors are available for an SRv6 SID:

· PSP—The penultimate SRv6 node removes the SRH to reduce the workload of the endpoint SRv6 node and improve forwarding efficiency. The endpoint SRv6 node does not read the SRH, and it only looks up the local SID table for the destination IPv6 address of packets to forward the packets.

· NO PSP—The penultimate SRv6 node does not remove the SRH. The endpoint SRv6 node reads the SRH and executes the function of the SID in the SRH.

Restrictions and guidelines

For the flavor change to take effect, you must reboot the cards that participate in SRv6 services.

You can use the flavor-mode switch no-psp or opcode command to change the SRv6 SID flavor. The flavor-mode switch no-psp command takes effect on all SIDs. The opcode command takes effect only on a specific SID. For an SID, the flavor-mode switch no-psp command takes precedence over the opcode command.

Procedure

1. Enter system view.

system-view

2. Enter SRv6 view.

segment-routing ipv6

3. Set the SRv6 SID flavor to NO-PSP.

flavor-mode switch no-psp

By default, the SRv6 SID flavor is PSP.

Setting the SRH encapsulation mode to normal encapsulation

About this task

SRv6 forwarding supports the following SRH encapsulation modes:

· Normal encapsulation mode—In this mode, the SRH includes all SIDs on the forwarding path. The device can obtain the complete path information from the SRH.

· Reduced encapsulation mode—In this mode, the SRH includes all SIDs except the first SID on the forwarding path. The first SID is encapsulated in the IPv6 header as the destination IPv6 address to reduce the SRH length.

For the SRH encapsulation mode setting to take effect, you must reboot the card that participates in SRv6 services.

Procedure

1. Enter system view.

system-view

2. Enter SRv6 view.

segment-routing ipv6

3. Set the SRH encapsulation mode to normal encapsulation.

srh-mode switch normal

By default, the SRH encapsulation mode is reduced encapsulation.

Configuring dynamic End.X SID deletion delay

About this task

Packet loss occurs between OSPFv3 or IS-IS neighbors if the neighbors frequently delete and request dynamically allocated End.X SIDs for the links between them because of neighbor flapping. To resolve this issue, set a delay timer for deleting dynamically allocated End.X SIDs when the neighbors are disconnected. If the neighbors are still disconnected when the delay timer expires, the device deletes the dynamically allocated End.X SIDs.

Restrictions and guidelines

The device always immediately deletes automatically allocated End.X SIDs without any delay in the following situations:

· The reset ospfv3 process command is executed. For more information about this command, see OSPFv3 commands in Layer 3—IP Routing Command Reference.

· The reset isis all command is executed. For more information about this command, see IS-IS commands in Layer 3—IP Routing Command Reference.

· Interfaces are deleted or removed. For example, an interface module is removed, or a subinterface or VLAN interface is deleted.

Procedure

1. Enter system view.

system-view

2. Enter IS-IS IPv6 address family view or OSPFv3 process view.

¡ Execute the following commands in sequence to enter IS-IS IPv6 address family view:

isis [ process-id ] [ vpn-instance vpn-instance-name ]

address-family ipv6 [ unicast ]

¡ Enter OSPFv3 process view.

ospfv3 [ process-id | vpn-instance vpn-instance-name ] *

3. Enable dynamic End.X SID deletion delay and set the delay time.

segment-routing ipv6 end-x delete-delay [ time-value ]

By default, dynamic End.X SID deletion delay is enabled and the delay time is 1800 seconds.

Specifying a source address for the outer IPv6 header of SRv6-encapsulated packets

Restrictions and guidelines

As a best practice to ensure correct traffic forwarding in an SRv6 network, specify a source address for the outer IPv6 header of SRv6-encapsulated packets.

You cannot specify a loopback address, link-local address, multicast address, or unspecified address as the source IPv6 address. You must specify an IPv6 address of the local device as the source IPv6 address, and make sure the IPv6 address has been advertised by a routing protocol. As a best practice, specify a loopback interface address of the local device as the source IPv6 address.

Procedure

1. Enter system view.

system-view

2. Enter SRv6 view.

segment-routing ipv6

3. Specify a source address for the outer IPv6 header of SRv6-encapsulated packets.

encapsulation source-address ipv6-address [ ip-ttl ttl-value ]

By default, no source address is specified for the outer IPv6 header of SRv6-encapsulated packets.

Using IGP to advertise SRv6 SIDs

About this task

Use an IGP protocol to advertise the SRv6 SIDs of a locator by applying the locator to the IGP protocol.

Prerequisites

If IS-IS is used to advertise SRv6 SIDs, make sure the cost style of IS-IS is wide, compatible, or wide-compatible. For more information about the cost styles of IS-IS, see Layer 3—IP Routing Configuration Guide.

Using IS-IS to advertise SRv6 SIDs

1. Enter system view.

system-view

2. Enter IS-IS process view.

isis [ process-id ] [ vpn-instance vpn-instance-name ]

3. Enter IS-IS IPv6 address family view.

address-family ipv6 [ unicast ]

4. Apply a locator to IS-IS IPv6 address family.

segment-routing ipv6 locator locator-name [ level-1 | level-2 ] [ auto-sid-disable ]

By default, no locators are applied to IS-IS IPv6 address family.

Repeat this command to apply multiple locators to IS-IS IPv6 address family for the family to advertise multiple SRv6 SIDs.

5. (Optional.) Configure IS-IS to advertise SRv6 SIDs for L3 services.

segment-routing ipv6 advertise l3-service-sid

By default, IS-IS does not advertise SRv6 SIDs for L3 services.

This command is supported only by the IS-IS processes in the public network.

This command enables IS-IS to advertise SRv6 SIDs for L3 services in LSPs. With this command, IS-IS reports link state information for L3 service-related SRv6 SIDs to the controller to meet the requirements for applications that need the information. IS-IS can advertise only End.DT4 SIDs, End.DT6 SIDs, and End.DT46 SIDs in the current software version.

Using OSPFv3 to advertise SRv6 SIDs

1. Enter system view.

system-view

2. Enter OSPFv3 process view.

ospfv3 [ process-id | vpn-instance vpn-instance-name ] *

3. Apply a locator to the OSPFv3 process.

segment-routing ipv6 locator locator-name [ auto-sid-disable ]

By default, no locators are applied to an OSPFv3 process.

Repeat this command to apply multiple locators to the OSPFv3 process for the process to advertise multiple SRv6 SIDs.

Enabling BGP to advertise routes for a locator

About this task

Perform this task in an inter-AS BGP network. This task enables the device to generate routes for a locator in the BGP IPv6 unicast routing table and use BGP to advertise the routes to BGP peers.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Enter BGP IPv6 unicast address family view.

address-family ipv6 [ unicast ]

4. Configure the device to generate routes for the specified locator in the BGP IPv6 unicast routing table and advertise the routes to BGP peers.

advertise srv6 locator locator-name [ route-policy route-policy-name ]

By default, the device does not generate routes for a locator in the BGP IPv6 unicast routing table.

Configuring BGP-EPE

Enabling SRv6 BGP-EPE

About this task

BGP-EPE allocates BGP peer SIDs to inter-AS segments. The device advertises the peer SIDs to a network controller through BGP LS messages. The controller orchestrates the IGP SIDs and BGP peer SIDs to realize optimal inter-AS traffic forwarding.

With this feature, the device can allocate SRv6 SIDs to its connected BGP peers or peer groups to identify its connected BGP peers or links.

Restrictions and guidelines

If you do not specify any parameters for the peer egress-engineering srv6 command, the device will dynamically allocate SRv6 SIDs to peers. The SRv6 SIDs belong to the locator specified by using the segment-routing ipv6 egress-engineering locator command in BGP instance view.

When you use the peer egress-engineering srv6 command for a peer, follow these restrictions and guidelines:

· If you use this command to specify multiple locators for that peer, only the most recent configuration takes effect.

· If you use this command to specify multiple static SRv6 SIDs and the SIDs belong to different types, all types of SRv6 SIDs can take effect. For the same type of SRv6 SIDs, only the most recent configuration takes effect.

If you specify a static SRv6 SID for a peer, the specified static SRv6 SID must belong to the locator specified by using the segment-routing ipv6 egress-engineering locator command in BGP instance view.

If you specify a static SRv6 SID for a peer, the specified static SRv6 SID must belong to the locator specified using the segment-routing ipv6 egress-engineering locator command in BGP instance view. To identify whether the static SRv6 SID takes effect, use the display bgp egress-engineering ipv6 command. If the static SRv6 SID does not take effect, the static SRv6 SID has been used by other protocols. Before the static SRv6 SID is released, BGP-EPE does not allocate a dynamic SRv6 SID. After the static SRv6 SID is released, first use the undo peer egress-engineering srv6 command to remove the original static SRv6 SID configuration. Then, use the peer egress-engineering srv6 command to reconfigure the static SRv6 SID.

The static SRv6 SIDs specified by using the following commands cannot be the same:

· peer egress-engineering srv6.

· egress-engineering srv6 peer-set.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Enable SRv6 BGP-EPE.

peer group-name egress-engineering srv6

peer ipv6-address [ prefix-length ] egress-engineering srv6 [ locator locator-name | static-sid { psp psp-sid | no-psp-usp no-psp-usp-sid } * ]

By default, SRv6 BGP-EPE is disabled.

Applying a locator to BGP-EPE

About this task

Perform this task to restrict the range of End.X SIDs that can be allocated to BGP-EPE SRv6 peer sets and BGP-EPE-enabled peers in a BGP instance. All static SRv6 SIDs configured for the BGP-EPE SRv6 peer sets and peers must belong to the locator specified by performing this task.

Restrictions and guidelines

To dynamically allocate End.X SIDs from the specified locator:

· Do not configure a static SRv6 SID when you create a BGP-EPE SRv6 peer set by using the egress-engineering srv6 peer-set command.

· Do not specify a locator or configure a static SRv6 SID when you enable SRv6 BGP-EPE for a peer by using the peer egress-engineering srv6 command.

When you apply a locator to BGP-EPE, BGP-EPE takes the following actions:

· If static SRv6 SIDs are configured in the locator, BGP-EPE preferentially uses static SRv6 SIDs.

· If the static SRv6 SIDs configured in the locator are End.X SIDs with the same opcode and different output interfaces and next hops, BGP-EPE does not use the static SRv6 SIDs but dynamically collocates SRv6 SIDs.

· If no static SRv6 SIDs are configured, BGP-EPE dynamically allocates SRv6 SIDs.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Apply a locator to BGP-EPE.

segment-routing ipv6 egress-engineering locator locator-name

By default, no locator is applied to BGP-EPE.

Configuring a BGP-EPE SRv6 peer set

About this task

If the device establishes BGP peer relationship with multiple devices, perform this task to add the peer devices to a peer set and allocate a PeerSet SID to the peer set. When the device forwards traffic based on the PeerSet SID, it distributes the traffic among the peers for load sharing.

Prerequisites

Enable SRv6 BGP-EPE on all peers that will be added to the BGP-EPE SRv6 peer set.

Use the segment-routing ipv6 egress-engineering locator command in BGP instance view to apply a locator to BGP-EPE.

· If automatic SID allocation is used, the device dynamically allocates an SRv6 SID to the BGP-EPE SRv6 peer set from the specified locator.

· If you specify a static SRv6 SID for the BGP-EPE SRv6 peer set, the specified static SRv6 SID must belong to the specified locator.

If you execute the egress-engineering srv6 peer-set command to specify multiple SRv6 SIDs for one peer set, the effective configuration depends on whether the SRv6 SIDs are the same type.

· If all the SRv6 SIDs belong to the same type, only the most recent configuration takes effect.

· If the SRv6 SIDs belong to different types, the configuration for all the SRv6 SID types takes effect. For the SRv6 SIDs that belong to the same type, only the most recent configuration takes effect. Make sure each SRv6 SID is unique among all the SRv6 SID types.

The static SRv6 SIDs configured by using the following commands cannot be the same:

· egress-engineering srv6 peer-set.

· peer egress-engineering srv6.

Procedure

1. Enter system view.

system-view

2. Enter BGP instance view.

bgp as-number [ instance instance-name ]

3. Create a BGP-EPE SRv6 peer set.

egress-engineering srv6 peer-set peer-set-name [ static-sid { psp psp-sid | no-psp-usp no-psp-usp-sid } * ]

4. Add a peer to the BGP-EPE SRv6 peer set.

peer { ipv6-address [ prefix-length ] } peer-set srv6-peer-set-name

By default, no peers are added to a BGP-EPE SRv6 peer set.

To change the BGP-EPE SRv6 peer set for a peer, you must first use undo peer peer-set command to remove that peer from the original BGP-EPE SRv6 peer set.

Configuring traffic forwarding statistics collection for local SRv6 SIDs

About this task

Perform this task to enable traffic forwarding statistics collection for local SRv6 SIDs and set the statistics collection interval to facilitate SRv6 traffic prediction and optimization.

Procedure

1. Enter system view.

system-view

2. Enter SRv6 view.

segment-routing ipv6

3. Enable traffic forwarding statistics collection for local SRv6 SIDs.

local-sid forwarding statistics enable

By default, traffic forwarding statistics collection is disabled for local SRv6 SIDs.

4. (Optional.) Set the interval at which traffic forwarding statistics are collected for local SRv6 SIDs.

local-sid forwarding statistics interval interval

By default, traffic forwarding statistics are collected at intervals of 30 seconds for local SRv6 SIDs.

Configuring TI-LFA FRR

TI-LFA FRR tasks at a glance

To configure TI-LFA FRR, perform the following tasks:

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 FRR microloop avoidance

4. (Optional.) Configuring SR microloop avoidance

Enabling TI-LFA FRR

Enabling IPv6 IS-IS TI-LFA FRR

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv6 unicast address family view.

address-family ipv6

4. Enable LFA FRR for IPv6 IS-IS.

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

By default, LFA FRR is disabled for IPv6 IS-IS.

5. Enable TI-LFA FRR for IPv6 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 IPv6 IS-IS.

6. (Optional.) Set the priority for an FRR backup path selection policy.

fast-reroute tiebreaker { lowest-cost | node-protecting | srlg-disjoint } preference preference [ level-1 | level-2 ]

By default, the priority values of the lowest-cost, node-protection, and SRLG-disjoint backup path selection policies are 20, 40, and 10, respectively.

Enabling OSPFv3 TI-LFA FRR

1. Enter system view.

system-view

2. Enter OSPFv3 view.

ospfv3 [ process-id | vpn-instance vpn-instance-name ] *

3. Enable LFA FRR for OSPFv3.

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

By default, LFA FRR is disabled for OSPFv3.

4. Enable TI-LFA FRR for OSPFv3.

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

By default, TI-LFA FRR is disabled for OSPFv3.

5. (Optional.) Set the priority for FRR backup path selection policies.

fast-reroute tiebreaker { lowest-cost | node-protecting } preference preference

By default, the priority values of the lowest-cost and node-protection backup path selection policies are 20 and 40, respectively.

Disabling an interface from participating in TI-LFA calculation

Disabling an IPv6 IS-IS interface from participating in TI-LFA calculation

1. Enter system view.

system-view

2. Enter the view of IPv6 IS-IS interface.

interface interface-type interface-number

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

isis ipv6 fast-reroute ti-lfa disable [ level-1 | level-2 ]

By default, an IPv6 IS-IS interface participates in TI-LFA calculation.

Disabling an OSPFv3 interface from participating in TI-LFA calculation

1. Enter system view.

system-view

2. Enter the view of OSPFv3 interface.

interface interface-type interface-number

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

ospfv3 fast-reroute ti-lfa disable [ instance instance-id ]

By default, an OSPFv3 interface participates in TI-LFA calculation.

Configuring FRR microloop avoidance

About this task

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 a device along the backup path has not finished route convergence, a traffic loop will occur. Traffic will be looped between the device and the source node (the node prior to the node or link that failed) until the device finishes route convergence.

To resolve this issue, configure this feature on a node enabled with TI-LFA FRR. FRR microloop avoidance first switches traffic to the backup path calculated by TI-LFA to avoid packet loss after a node or link failure on the optimal path. Then, that node starts an FRR microloop avoidance RIB-update-delay timer configured by the fast-reroute microloop-avoidance rib-update-delay command after it finishes route convergence. The node performs the following operations only after all nodes on the backup path finish route convergence and the timer times out:

· Issues the forwarding path after route convergence to the FIB.

· Switches traffic from the backup path calculated by TI-LFA to the forwarding path after route convergence.

Restrictions and guidelines

If you configure both FRR microloop avoidance and SR microloop avoidance, FRR microloop avoidance takes precedence over SR microloop avoidance. The FRR microloop avoidance RIB-update-delay timer and SR microloop avoidance RIB-update-delay timer are started for the two features, respectively. The following situations exist depending on the configuration of the two timers:

· If the FRR microloop avoidance RIB-update-delay timer is equal to or greater than the SR microloop avoidance RIB-update-delay timer, traffic is switched to the post-convergence path immediately when the former timer times out.

· If the FRR microloop avoidance RIB-update-delay timer is larger than the SR microloop avoidance RIB-update-delay timer, traffic is switched to the post-convergence path until after the latter timer times out.

Procedure

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv6 unicast address family view.

address-family ipv6

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 SR microloop avoidance

About this task

SR microloop avoidance provides microloop avoidance after both a network failure and a failure recovery.

After a network failure occurs or recovers, route convergence occurs on relevant network devices. Because of nonsimultaneous 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.

Microloop avoidance after a network failure and a failure recovery is as follows:

· When a network failure occurs, a node enabled with this feature issues the calculated forwarding path to the FIB after route convergence and switches the traffic to the forwarding path after the delay timer times out. Before the timer times out, traffic is forwarded along the TI-LFA FRR backup path to avoid microloops.

· When the failure recovers, a node enabled with this feature also calculates an explicit path that contains SIDs except for the primary forwarding path. Before the timer times out, traffic is forwarded along the backup path to avoid microloops.

To ensure sufficient time for IGP to complete route convergence, set the SR microloop avoidance RIB-update-delay time. Before the timer expires, faulty relevant devices will forward traffic along the specified path. Upon expiration of the timer and completion of IGP route convergence, traffic will traverse along the IGP-calculated path.

Restrictions and guidelines

Configuring IPv6 IS-IS SR microloop avoidance

1. Enter system view.

system-view

2. Enter IS-IS view.

isis process-id

3. Enter IS-IS IPv6 unicast address family view.

address-family ipv6

4. Enable SR microloop avoidance for IPv6 IS-IS.

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

By default, SR microloop avoidance is disabled for IPv6 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.

Configuring OSPFv3 SR microloop avoidance

1. Enter system view.

system-view

2. Enter OSPFv3 process view.

ospfv3 [ process-id | vpn-instance vpn-instance-name ] *

3. Enable SR microloop avoidance for OSPFv3.

segment-routing microloop-avoidance enable

By default, SR microloop avoidance is disabled for OSPFv3.

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

segment-routing microloop-avoidance rib-update-delay delay-time

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

Configuring the SRv6 MTU

About this task

Perform this task to configure one of the following MTUs:

· Path MTU—The maximum IPv6 MTU along the path from the source node to the destination node. The transit nodes do not fragment SRv6 tunneled packets. If a packet is larger than the MTU of the output interface, the packet will be discarded. If the MTU is too small, the bandwidth is not sufficiently used. To address these issues, configure an appropriate SRv6 path MTU.

· Reserved MTU—Reserved MTU on the source node for TI-LFA. When packets are switched to the backup path after the primary path fails, the device reconstructs an IPv6 header and SRH for the packets. As a result, packet drop might occur because the packet size has exceeded the MTU. To resolve this issue, configure a reserved MTU on the source node to reserve bytes for adding a new SRH to SRv6 packets in case of primary path failure.

The SRv6 path MTU minus the reserved MTU is the active MTU. The effective MTU for SRv6 packets on the source node is the smaller value from the following values:

· The active MTU.

· The IPv6 MTU of the physical output interface.

Restrictions and guidelines

Make sure the active MTU is equal to or greater than 1280 bytes.

Procedure

1. Enter system view.

system-view

2. Enter SRv6 view.

segment-routing ipv6

3. Specify a reserved MTU for SRv6 path MTU.

path-mtu reserved [ reserved-value ]

By default, no reserved MTU is specified for SRv6 path MTU.

4. Configure the SRv6 path MTU.

path-mtu mtu-value

By default, the SRv6 path MTU is 9000 bytes.

Configuring the SRv6 DiffServ mode

About this task

SRv6 DiffServ mode determines how an SRv6 node processes the IP precedence and DSCP for packets forwarded between an IP network and an SRv6 network. The device supports the following SRv6 DiffServ modes:

· Pipe mode—When a packet enters the SRv6 network, the ingress node adds a new IPv6 header to the original packet. The ingress node ignores the IP precedence or DSCP value in the original packet and uses the value specified by using the service-class argument as the traffic class in the new IPv6 header. In the SRv6 network, SRv6 nodes perform QoS scheduling for the packet based on the specified traffic class. When the packet leaves the SRv6 network, the egress node removes the outer IPv6 header from the packet without modifying the IP precedence or DSCP value in the original packet.

· Short-pipe mode—When a packet enters and leaves the SRv6 network, all SRv6 nodes process the packet in the same way as in pipe mode except for the egress node. After the egress node removes the outer IPv6 header from the packet, it performs QoS scheduling as follows:

¡ If no priority trust mode is configured, the egress node performs QoS scheduling for the packet based on the IP precedence or DSCP value in the original packet.

¡ If a priority trust mode is configured, the egress node performs QoS scheduling for the packet based on the trusted priority.

· Uniform mode—When a packet enters the IPv6 network, the ingress node maps the IP precedence or DSCP value in the original IP header to the outer IPv6 header as the traffic class. When the packet leaves the SRv6 network, the egress node maps the traffic class value in the outer IPv6 header to the original packet as the IP precedence or DSCP value.

Restrictions and guidelines

When you configure the SRv6 DiffServ mode on the source and destination nodes of an SRv6 tunnel, follow these restrictions and guidelines:

· The outbound DiffServ mode on the local end must be the same as the inbound DiffServ mode on the peer end.

· The inbound DiffServ mode on the local end must be the same as the outbound DiffServ mode on the peer end.

For more information about IP precedence and DSCP, see priority mapping configuration in QoS Configuration Guide.

Procedure

1. Enter system view.

system-view

2. Enter SRv6 view.

segment-routing ipv6

3. Configure the SRv6 DiffServ mode.

diffserv-mode { ingress { pipe service-class | short-pipe service-class | uniform } egress { pipe | short-pipe | uniform } | { pipe service-class | short-pipe service-class | uniform } }

By default, no SRv6 DiffServ mode is configured.

Verifying and maintaining SRv6

Displaying basic SRv6 configuration information

Perform display tasks in any view.

· Display brief SRv6 information.

display segment-routing ipv6 brief

· Display SRv6 forwarding entries.

display segment-routing ipv6 forwarding [ entry-id ] [ slot slot-number ]

· Display information about the SRv6 local SID forwarding table.

display segment-routing ipv6 local-sid [ locator locator-name ] [ end-x [ sid | interface interface-type interface-number [ nexthop nexthop-ipv6-address ] ] ] [ owner owner ]

· Display statistics about SRv6 SIDs allocated for each protocol.

display segment-routing ipv6 local-sid statistics [ locator [ locator-name ] ]

· Display SRv6 locator information.

display segment-routing ipv6 locator [ locator-name ]

· Display available static SRv6 SIDs in a locator.

display segment-routing ipv6 available-static-sid locator locator-name [ from begin-value ]

· Display SRv6 locator configuration and statistics about allocated SRv6 SIDs in locators.

display segment-routing ipv6 locator-statistics [ locator-name ]

Displaying SRv6 BGP-EPE information

Perform display tasks in any view.

· Display BGP-EPE information for IPv6 peers.

display bgp [ instance instance-name ] egress-engineering ipv6 [ ipv6-address ] [ verbose ]

· Display information about BGP-EPE SRv6 peer sets.

display bgp [ instance instance-name ] egress-engineering srv6 peer-set [ srv6-peer-set-name ]

Displaying IS-IS SRv6 information

Perform display tasks in any view.

· Display IS-IS SRv6 capability information.

display isis segment-routing ipv6 capability [ level-1 | level-2 ] [ process-id ]

· Display IS-IS SRv6 locator routing information.

display isis segment-routing ipv6 locator [ ipv6-address prefix-length ] [ [ level-1 | level-2 ] | verbose ] * [ process-id ]

· Display information about SRv6 SIDs advertised by IS-IS.

· Display information about SRv6 SIDs advertised by IS-IS in a locator or all locators.

· Display information about SRv6 SIDs advertised from a system or all systems.

· Display information about conflicting SRv6 SIDs.

display isis segment-routing ipv6 sid-info conflict [ sid-value ] [ level-1 | level-2 ] [ process-id ]

· Display SRv6 SID statistics.

display isis segment-routing ipv6 sid-info statistics [ system-id system-id ] [ level-1 | level-2 ] [ process-id ]

Displaying OSPFv3 SRv6 information

Perform display tasks in any view.

· Display OSPFv3 SRv6 capability information.

display ospfv3 [ process-id ] segment-routing ipv6 capability

· Display OSPFv3 SRv6 locator information.

display ospfv3 [ process-id ] segment-routing ipv6 locator [ ipv6-address prefix-length ]

Displaying and clearing traffic forwarding statistics for local SRv6 SIDs

Displaying traffic forwarding statistics for local SRv6 SIDs

To display traffic forwarding statistics for local SRv6 SIDs, execute the following commands in any view:

display segment-routing ipv6 local-sid forwarding statistics { end | end-dt2m | end-dt2u | end-dt2ul } [ sid ]

display segment-routing ipv6 local-sid forwarding statistics { end-dt4 | end-dt46 | end-dt6 | end-dx4 | end-dx6 } [ sid | vpn-instance vpn-instance-name ]

display segment-routing ipv6 local-sid forwarding statistics end-x [ sid | interface interface-type interface-number [ nexthop nexthop-ipv6-address ] ]

Clearing traffic forwarding statistics for local SRv6 SIDs

To clear traffic forwarding statistics for local SRv6 SIDs, execute the following command in user view:

reset segment-routing ipv6 local-sid forwarding statistics

SRv6 configuration examples

Example: Configuring IPv6 IS-IS TI-LFA FRR

Network configuration

As shown in Figure 11, complete the following tasks to implement TI-LFA FRR:

· Configure IPv6 IS-IS on Device A, Device B, Device C, and Device D to achieve network level connectivity.

· Configure IS-IS SRv6 on Device A, Device B, Device C, and Device D.

· Configure TI-LFA FRR to remove the loop on Link B and to implement fast traffic switchover to Link B when Link A fails.

Figure 11 Network diagram

‌

Table 1 Interface and IP address assignment

Device	Interface	IP address	Device	Interface	IP address
Device A	Loop1	1::1/128	Device B	Loop1	2::2/128
	HGE1/0/1	2000:1::1/64		HGE1/0/1	2000:1::2/64
	HGE1/0/2	2000:4::1/64		HGE1/0/2	2000:2::2/64
Device C	Loop1	3::3/128	Device D	Loop1	4::4/128
	HGE1/0/1	2000:3::3/64		HGE1/0/1	2000:3::4/64
	HGE1/0/2	2000:2::3/64		HGE1/0/2	2000:4::4/64

Prerequisites

By default, interfaces on the device are in administratively down state. Use the undo shutdown command to bring up interfaces as needed in the corresponding interface view.

Procedure

1. Configure IPv6 addresses and prefixes for interfaces. (Details not shown.)

2. Configure Device A:

# Configure IPv6 IS-IS to achieve network level connectivity and set the IS-IS cost style to wide.

<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] address-family ipv6

[DeviceA-isis-1-ipv6] quit

[DeviceA-isis-1] quit

[DeviceA] interface hundredgige 1/0/1

[DeviceA-HundredGigE1/0/1] isis ipv6 enable 1

[DeviceA-HundredGigE1/0/1] isis cost 100

[DeviceA-HundredGigE1/0/1] quit

[DeviceA] interface hundredgige 1/0/2

[DeviceA-HundredGigE1/0/2] isis ipv6 enable 1

[DeviceA-HundredGigE1/0/2] isis cost 10

[DeviceA-HundredGigE1/0/2] quit

[DeviceA] interface loopback 1

[DeviceA-LoopBack1] isis ipv6 enable 1

[DeviceA-LoopBack1] quit

# Enable SRv6 and configure a locator.

[DeviceA] segment-routing ipv6

[DeviceA-segment-routing-ipv6] locator aaa ipv6-prefix 11:: 64 static 32

[DeviceA-segment-routing-ipv6-locator-aaa] quit

[DeviceA-segment-routing-ipv6] quit

# Configure IPv6 IS-IS TI-LFA FRR.

[DeviceA] isis 1

[DeviceA-isis-1] address-family ipv6

[DeviceA-isis-1-ipv6] fast-reroute lfa

[DeviceA-isis-1-ipv6] fast-reroute ti-lfa

[DeviceA-isis-1-ipv6] fast-reroute microloop-avoidance enable

[DeviceA-isis-1-ipv6] segment-routing microloop-avoidance enable

[DeviceA-isis-1-ipv6] quit

[DeviceA-isis-1] quit

# Apply the locator to the IPv6 IS-IS process.

[DeviceA] isis 1

[DeviceA-isis-1] address-family ipv6

[DeviceA-isis-1-ipv6] segment-routing ipv6 locator aaa

[DeviceA-isis-1-ipv6] quit

[DeviceA-isis-1] quit

3. Configure Device B:

# Configure IPv6 IS-IS to achieve network level connectivity and set the IS-IS cost style to wide.

<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] address-family ipv6

[DeviceB-isis-1-ipv6] quit

[DeviceB-isis-1] quit

[DeviceB] interface hundredgige 1/0/1

[DeviceB-HundredGigE1/0/1] isis ipv6 enable 1

[DeviceB-HundredGigE1/0/1] isis cost 10

[DeviceB-HundredGigE1/0/1] quit

[DeviceB] interface hundredgige 1/0/2

[DeviceB-HundredGigE1/0/2] isis ipv6 enable 1

[DeviceB-HundredGigE1/0/2] isis cost 10

[DeviceB-HundredGigE1/0/2] quit

[DeviceB] interface loopback 1

[DeviceB-LoopBack1] isis ipv6 enable 1

[DeviceB-LoopBack1] quit

# Enable SRv6 and configure a locator.

[DeviceB] segment-routing ipv6

[DeviceB-segment-routing-ipv6] locator bbb ipv6-prefix 22:: 64 static 32

[DeviceB-segment-routing-ipv6-locator-bbb] quit

[DeviceB-segment-routing-ipv6] quit

# Enable IPv6 IS-IS TI-LFA FRR.

[DeviceB] isis 1

[DeviceB-isis-1] address-family ipv6

[DeviceB-isis-1-ipv6] fast-reroute lfa

[DeviceB-isis-1-ipv6] fast-reroute ti-lfa

# Apply the locator to the IPv6 IS-IS process.

[DeviceB-isis-1-ipv6] segment-routing ipv6 locator bbb

[DeviceB-isis-1-ipv6] quit

[DeviceB-isis-1] quit

4. Configure Device C:

# Configure IPv6 IS-IS to achieve network level connectivity and set the IS-IS cost style to wide.

<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] address-family ipv6

[DeviceC-isis-1-ipv6] quit

[DeviceC-isis-1] quit

[DeviceC] interface hundredgige 1/0/1

[DeviceC-HundredGigE1/0/1] isis ipv6 enable 1

[DeviceC-HundredGigE1/0/1] isis cost 10

[DeviceC-HundredGigE1/0/1] quit

[DeviceC] interface hundredgige 1/0/2

[DeviceC-HundredGigE1/0/2] isis ipv6 enable 1

[DeviceC-HundredGigE1/0/2] isis cost 100

[DeviceC-HundredGigE1/0/2] quit

[DeviceC] interface loopback 1

[DeviceC-LoopBack1] isis ipv6 enable 1

[DeviceC-LoopBack1] quit

# Enable SRv6 and configure a locator.

[DeviceC] segment-routing ipv6

[DeviceC-segment-routing-ipv6] locator ccc ipv6-prefix 33:: 64 static 32

[DeviceC-segment-routing-ipv6-locator-ccc] quit

[DeviceC-segment-routing-ipv6] quit

# Enable IPv6 IS-IS TI-LFA FRR.

[DeviceC] isis 1

[DeviceC-isis-1] address-family ipv6

[DeviceC-isis-1-ipv6] fast-reroute lfa

[DeviceC-isis-1-ipv6] fast-reroute ti-lfa

# Apply the locator to the IPv6 IS-IS process.

[DeviceC-isis-1-ipv6] segment-routing ipv6 locator ccc

[DeviceC-isis-1-ipv6] quit

[DeviceC-isis-1] quit

5. Configure Device D:

# Configure IPv6 IS-IS to achieve network level connectivity and set the IS-IS cost style to wide.

<DeviceD> system-view

[DeviceD] isis 1

[DeviceD-isis-1] network-entity 00.0000.0000.0004.00

[DeviceD-isis-1] cost-style wide

[DeviceD-isis-1] address-family ipv6

[DeviceD-isis-1-ipv6] quit

[DeviceD-isis-1] quit

[DeviceD] interface hundredgige 1/0/1

[DeviceD-HundredGigE1/0/1] isis ipv6 enable 1

[DeviceD-HundredGigE1/0/1] isis cost 100

[DeviceD-HundredGigE1/0/1] quit

[DeviceD] interface hundredgige 1/0/2

[DeviceD-HundredGigE1/0/2] isis ipv6 enable 1

[DeviceD-HundredGigE1/0/2] isis cost 10

[DeviceD-HundredGigE1/0/2] quit

[DeviceD] interface loopback 1

[DeviceD-LoopBack1] isis ipv6 enable 1

[DeviceD-LoopBack1] quit

# Enable SRv6 and configure a locator.

[DeviceD] segment-routing ipv6

[DeviceD-segment-routing-ipv6] locator ddd ipv6-prefix 44:: 64 static 32

[DeviceD-segment-routing-ipv6-locator-ddd] quit

[DeviceD-segment-routing-ipv6] quit

# Enable IPv6 IS-IS TI-LFA FRR.

[DeviceD] isis 1

[DeviceD-isis-1] address-family ipv6

[DeviceD-isis-1-ipv6] fast-reroute lfa

[DeviceD-isis-1-ipv6] fast-reroute ti-lfa

# Apply the locator to the IPv6 IS-IS process.

[DeviceD-isis-1-ipv6] segment-routing ipv6 locator ddd

[DeviceD-isis-1-ipv6] quit

[DeviceD-isis-1] quit

Verifying the configuration

# Display IPv6 IS-IS routing information for 3::3/128.

[DeviceA] display isis route ipv6 3::3 128 verbose

Route information for IS-IS(1)

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

Level-1 IPv6 forwarding table

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

IPv6 dest : 3::3/128

Flag : R/L/- Cost : 20

Admin tag : - Src count : 2

Nexthop : FE80::4449:7CFF:FEE0:206

Interface : HGE1/0/1

TI-LFA:

Interface : HGE1/0/2

BkNextHop : FE80::4449:91FF:FE42:407

LsIndex : 0x80000001

Backup label stack(top->bottom): {44::1:0:1}

Nib ID : 0x24000006

Flags: D-Direct, R-Added to Rib, L-Advertised in LSPs, U-Up/Down Bit Set

The output shows TI-LFA backup next hop information.

10-Segment Routing Configuration Guide

Basic concepts

SR node

SID

SRv6 SID flavors

Local SID forwarding table

Segment List

BGP-EPE

TI-LFA FRR background

TI-LFA FRR concepts

Protocols and standards

Prerequisites for SRv6

Configuring SRv6 SIDs

Restrictions and guidelines

Procedure

About this task

Restrictions and guidelines

Procedure

About this task

Procedure

About this task

Restrictions and guidelines

Procedure

Specifying a source address for the outer IPv6 header of SRv6-encapsulated packets

Restrictions and guidelines

Procedure

About this task

Prerequisites

Using IS-IS to advertise SRv6 SIDs

Using OSPFv3 to advertise SRv6 SIDs

About this task

Procedure

About this task

Restrictions and guidelines

Procedure

About this task

Restrictions and guidelines

Procedure

About this task

Prerequisites

Procedure

About this task

Procedure

Configuring TI-LFA FRR

Enabling IPv6 IS-IS TI-LFA FRR

Disabling an IPv6 IS-IS interface from participating in TI-LFA calculation

About this task

Restrictions and guidelines

Procedure

About this task

Restrictions and guidelines

Configuring IPv6 IS-IS SR microloop avoidance

Configuring OSPFv3 SR microloop avoidance

About this task

Restrictions and guidelines

Procedure

About this task

Restrictions and guidelines

Procedure

Verifying and maintaining SRv6

Displaying traffic forwarding statistics for local SRv6 SIDs

Clearing traffic forwarding statistics for local SRv6 SIDs

Network configuration

Prerequisites

Procedure

Verifying the configuration

Cloud & AI

InterConnect

Intelligent Terminal Products

Product Support Services

Technical Service Solutions

Resource Center

Policy

Online Help

Become a Partner

Partner Resources

Partner Business Management

Company Information

News & Events

Contact Us