The configuration examples in this document were created and verified in a lab environment, and all the devices were started with the factory default configuration. When you are working on a live network, make sure you understand the potential impact of every command on your network.

This document assumes that you have basic knowledge of BFD, VRRP, Track, OSPF, and IS-IS.

General restrictions and guidelines

When you configure BFD, follow these restrictions and guidelines:

· IP tunnels (for example, IPv6 over IPv4 tunnels) do not support BFD.

· For BFD to work correctly on an interface, do not enable easy IP on the interface.

· For BFD to work correctly on a Layer 3 Ethernet subinterface or Layer 3 aggregate subinterface, do not configure QinQ on the subinterface.

· For BFD to work correctly on an aggregate interface after adding or removing a member port, shut down the port before the adding or removing operation.

Example: Configuring VRRP-BFD-Track collaboration

Network configuration

As shown in Figure 1:

· Two distribution layer devices, Device A and Device B, are deployed at the egress of area A and area B.

· Device A and Device B belong to VRRP group 1 and VRRP group 2.

· Device A is the master in VRRP group 1. Device B is the master in VRRP group 2.

· The default gateway is VRRP group 1 for users in area A and VRRP group 2 for users in area B.

Configure VRRP-Track-BFD collaboration to meet the following requirements:

· When Device A and Device B are operating correctly, they forward traffic for users in area A and area B, respectively.

· When one gateway device or the uplink of the device fails, BFD can detect the failure and the other device takes over to implement link switchover.

· When the downlink of a gateway device fails, L2 Switch A or L2 Switch B forwards user traffic to the gateway through interface Ten-GigabitEthernet 3/1/2. When the fault is cleared, L2 Switch A or L2 Switch B forwards user traffic to the gateway through interface Ten-GigabitEthernet 3/1/1.

Figure 1 Network diagram

Analysis

To meet the network requirements, you must perform the following tasks:

· For Device A to become the master in VRRP group 1, configure a higher priority (110) for Device A in VRRP group 1 (Device B uses the default priority 100). For Device B to become the master in VRRP group 2, configure a higher priority (110) for Device B in VRRP group 2 (Device A uses the default priority 100).

· To enable the failed master to forward traffic when it recovers, configure both VRRP groups to operate in preemptive mode.

· To prevent MSTP from blocking uplink interface Ten-GigabitEthernet 3/1/1 of Device A and Device B, disable the spanning tree feature on the interfaces.

Restrictions and guidelines

When you configure VRRP-BFD-Track collaboration, follow these restrictions and guidelines:

· Make sure the VRRP versions on all devices of the VRRP group are the same.

· The source IP address for BFD echo packets cannot be on the same network segment as any local interface's IP address. Otherwise, a large number of ICMP redirect packets might be sent from the peer, resulting in link congestion.

· The virtual IP address of an IPv4 VRRP group and the downlink interface IP address of the VRRP group must be in the same subnet. Otherwise, the hosts in the subnet might fail to access external networks.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ip address 1.1.1.1 24

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring static routes from Device E and Device F to the virtual IP addresses of the VRRP groups

1. Configure Device E:

Configure static routes to the virtual IP addresses of VRRP group 1 and VRRP group 2.

<DeviceE> system-view

[DeviceE] ip route-static 10.1.1.0 255.255.255.0 1.1.1.1

[DeviceE] ip route-static 10.1.2.0 255.255.255.0 1.1.1.1

2. Configure Device F:

Configure static routes to the virtual IP addresses of VRRP group 1 and VRRP group 2.

<DeviceF> system-view

[DeviceF] ip route-static 10.1.1.0 255.255.255.0 1.1.2.1

[DeviceF] ip route-static 10.1.2.0 255.255.255.0 1.1.2.1

Configuring VRRP groups

1. Configure Device A:

# Configure the virtual IP address for VRRP group 1, set the preemption delay, and configure the priority of Device A in VRRP group 1.

[DeviceA] interface ten-gigabitethernet 3/1/2

[DeviceA-Ten-GigabitEthernet3/1/2] vrrp vrid 1 virtual-ip 10.1.1.1

[DeviceA-Ten-GigabitEthernet3/1/2] vrrp vrid 1 priority 110

[DeviceA-Ten-GigabitEthernet3/1/2] vrrp vrid 1 preempt-mode delay 500

[DeviceA-Ten-GigabitEthernet3/1/2] quit

# Configure the virtual IP address for VRRP group 2, and set the preemption delay.

[DeviceA] interface ten-gigabitethernet 3/1/3

[DeviceA-Ten-GigabitEthernet3/1/3] vrrp vrid 2 virtual-ip 10.1.2.1

[DeviceA-Ten-GigabitEthernet3/1/3] vrrp vrid 2 preempt-mode delay 500

[DeviceA–Ten-GigabitEthernet3/1/3] quit

2. Configure Device B:

# Configure the virtual IP address for VRRP group 1, and set the preemption delay.

[DeviceB] interface ten-gigabitethernet 3/1/2

[DeviceB-Ten-GigabitEthernet3/1/2] vrrp vrid 1 virtual-ip 10.1.1.1

[DeviceB-Ten-GigabitEthernet3/1/2] vrrp vrid 1 preempt-mode delay 500

[DeviceB-Ten-GigabitEthernet3/1/2] quit

# Configure the virtual IP address for VRRP group 2, set the preemption delay, and configure the priority of Device B in VRRP group 2.

[DeviceB] interface ten-gigabitethernet 3/1/3

[DeviceB-Ten-GigabitEthernet3/1/3] vrrp vrid 2 virtual-ip 10.1.2.1

[DeviceB-Ten-GigabitEthernet3/1/3] vrrp vrid 2 priority 110

[DeviceB-Ten-GigabitEthernet3/1/3] vrrp vrid 2 preempt-mode delay 500

[DeviceB–Ten-GigabitEthernet3/1/3] quit

Configuring BFD

1. Configure Device A:

# Configure the source IP address for BFD echo packets.

[DeviceA] bfd echo-source-ip 10.10.10.10

2. Configure Device B:

# Configure the source IP address for BFD echo packets.

[DeviceB] bfd echo-source-ip 11.11.11.11

Configuring Track

1. Configure Device A:

# Create track entry 1, and associate it with the BFD session to verify the reachability of Device E.

[DeviceA] track 1 bfd echo interface ten-gigabitethernet 3/1/1 remote ip 1.1.1.2 local ip 1.1.1.1

# Associate VRRP group 1 with track entry 1 and decrease the router priority by 20 when the state of track entry 1 changes to negative.

[DeviceA] interface ten-gigabitethernet 3/1/2

[DeviceA-Ten-GigabitEthernet3/1/2] vrrp vrid 1 track 1 reduced 20

[DeviceA-Ten-GigabitEthernet3/1/2] quit

Configure Device B:

# Create track entry 1, and associate it with the BFD session to verify the reachability of Device F.

[DeviceB] track 1 bfd echo interface ten-gigabitethernet 3/1/1 remote ip 1.1.2.2 local ip 1.1.2.1

# Associate VRRP group 2 with track entry 1 and decrease the router priority by 20 when the state of track entry 1 changes to negative.

[DeviceB] interface ten-gigabitethernet 3/1/3

[DeviceB-Ten-GigabitEthernet3/1/3] vrrp vrid 2 track 1 priority reduced 20

[DeviceB-Ten-GigabitEthernet3/1/3] quit

Verifying the configuration

1. Verify that the hosts in the LAN can access the external network when Device A and Device B are operating correctly:

# Ping 1.1.1.2 from host A in area A.

<host A> ping 1.1.1.2

PING 1.1.1.2 (1.1.1.2): 56 data bytes

56 bytes from 1.1.1.2: seq=0 ttl=128 time=22.43 ms

56 bytes from 1.1.1.2: seq=1 ttl=128 time=7.17 ms

56 bytes from 1.1.1.2: seq=2 ttl=128 time=8.91 ms

56 bytes from 1.1.1.2: seq=3 ttl=128 time=7.45 ms

56 bytes from 1.1.1.2: seq=4 ttl=128 time=9.11 ms

--- 1.1.1.2 ping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max = 7.17/11.01/22.43 ms

# Ping 1.1.2.2 from host C in area B.

<host C> ping 1.1.2.2

PING 1.1.2.2 (1.1.2.2): 56 data bytes

56 bytes from 1.1.2.2: seq=0 ttl=128 time=22.43 ms

56 bytes from 1.1.2.2: seq=1 ttl=128 time=7.17 ms

56 bytes from 1.1.2.2: seq=2 ttl=128 time=8.91 ms

56 bytes from 1.1.2.2: seq=3 ttl=128 time=7.45 ms

56 bytes from 1.1.2.2: seq=4 ttl=128 time=9.11 ms

--- 1.1.2.2 ping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max = 7.17/11.01/22.43 ms

The output shows that the hosts in area A and area B can access the external network.

# Display BFD session information on Device A.

[DeviceA] display bfd session

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Echo Mode:

LD SourceAddr DestAddr State Holdtime Interface

65 1.1.1.1 1.1.1.2 Up 500ms XGE3/1/1

The output shows that a BFD session has been established.

# Display detailed VRRP group information on Device A.

[DeviceA] display vrrp verbose

IPv4 Virtual Router Information:

Running Mode : Standard

Total number of virtual routers : 2

Interface Ten-GigabitEthernet3/1/2

VRID : 1 Adver Timer : 100

Admin Status : Up State : Master

Config Pri : 110 Running Pri : 110

Preempt Mode : Yes Delay Time : 500

Auth Type : None

Virtual IP : 10.1.1.1

Virtual MAC : 0000-5e00-0101

Master IP : 10.1.1.101

VRRP Track Information:

Track Object : 1 State : Positive Pri Reduced : 20

Interface Ten-GigabitEthernet3/1/3

VRID : 2 Adver Timer : 100

Admin Status : Up State : Backup

Config Pri : 100 Running Pri : 100

Preempt Mode : Yes Delay Time : 500

Become Master : 3600ms left

Auth Type : None

Virtual IP : 10.1.2.1

Master IP : 10.1.2.102

# Display detailed VRRP group information on Device B.

[DeviceB] display vrrp verbose

IPv4 Virtual Router Information:

Running Mode : Standard

Total number of virtual routers : 2

Interface Ten-GigabitEthernet3/1/2

VRID : 1 Adver Timer : 100

Admin Status : Up State : Backup

Config Pri : 100 Running Pri : 100

Preempt Mode : Yes Delay Time : 500

Become Master : 3100ms left

Auth Type : None

Virtual IP : 10.1.1.1

Master IP : 10.1.1.101

Interface Ten-GigabitEthernet3/1/3

VRID : 2 Adver Timer : 100

Admin Status : Up State : Master

Config Pri : 110 Running Pri : 110

Preempt Mode : Yes Delay Time : 500

Auth Type : None

Virtual IP : 10.1.2.1

Virtual MAC : 0000-5e00-0102

Master IP : 10.1.2.102

VRRP Track Information:

Track Object : 1 State : Positive Pri Reduced : 20

The output shows the following information:

¡ In VRRP group 1, Device A is the master, and Device B is the backup. Hosts that use default gateway 10.1.1.1/24 access the Internet through Device A.

¡ In VRRP group 2, Device B is the master, and Device A is the backup. Hosts that use default gateway 10.1.2.1/24 access the Internet through Device B.

2. Verify that the hosts in the LAN can access the external network when the uplink monitored by Device A fails:

# Ping 1.1.1.2 from host A in area A.

<host A> ping 1.1.1.2

PING 1.1.1.2 (1.1.1.2): 56 data bytes

56 bytes from 1.1.1.2: seq=0 ttl=128 time=22.43 ms

56 bytes from 1.1.1.2: seq=1 ttl=128 time=7.17 ms

56 bytes from 1.1.1.2: seq=2 ttl=128 time=8.91 ms

56 bytes from 1.1.1.2: seq=3 ttl=128 time=7.45 ms

56 bytes from 1.1.1.2: seq=4 ttl=128 time=9.11 ms

--- 1.1.1.2 ping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max = 7.17/11.01/22.43 ms

# Ping 1.1.2.2 from host C in area B.

<host C> ping 1.1.2.2

PING 1.1.2.2 (1.1.2.2): 56 data bytes

56 bytes from 1.1.2.2: seq=0 ttl=128 time=22.43 ms

56 bytes from 1.1.2.2: seq=1 ttl=128 time=7.17 ms

56 bytes from 1.1.2.2: seq=2 ttl=128 time=8.91 ms

56 bytes from 1.1.2.2: seq=3 ttl=128 time=7.45 ms

56 bytes from 1.1.2.2: seq=4 ttl=128 time=9.11 ms

--- 1.1.2.2 ping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max = 7.17/11.01/22.43 ms

The output shows that the hosts in area A and area B can access the external network.

# Display BFD session information on Device A.

[DeviceA] display bfd session

Total Session Num: 1 Up Session Num: 0 Init Mode: Active

IPv4 Session Working Under Echo Mode:

LD SourceAddr DestAddr State Holdtime Interface

65 1.1.1.1 1.1.1.2 Down 0ms XGE3/1/1

The output shows that the BFD session has been terminated.

# Display detailed VRRP group information on Device B.

[DeviceB] display vrrp verbose

IPv4 Virtual Router Information:

Running Mode : Standard

Total number of virtual routers : 2

Interface Ten-GigabitEthernet3/1/2

VRID : 1 Adver Timer : 100

Admin Status : Up State : Master

Config Pri : 100 Running Pri : 100

Preempt Mode : Yes Delay Time : 500

Auth Type : None

Virtual IP : 10.1.1.1

Virtual MAC : 0000-5e00-0101

Master IP : 10.1.1.102

Interface Ten-GigabitEthernet3/1/3

VRID : 2 Adver Timer : 100

Admin Status : Up State : Master

Config Pri : 110 Running Pri : 110

Preempt Mode : Yes Delay Time : 500

Auth Type : None

Virtual IP : 10.1.2.1

Virtual MAC : 0000-5e00-0102

Master IP : 10.1.2.102

VRRP Track Information:

Track Object : 1 State : Positive Pri Reduced : 20

The output shows that Device B becomes the master in VRRP group 1. Hosts in area A access the external network through Device B.

# When the fault is cleared, display BFD session information on Device A.

[DeviceA] display bfd session

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Echo Mode:

LD SourceAddr DestAddr State Holdtime Interface

65 1.1.1.1 1.1.1.2 Up 1000ms XGE3/1/1

The output shows that the BFD session is resumed.

# Display detailed VRRP group information on Device A.

[DeviceA] display vrrp verbose

IPv4 Virtual Router Information:

Running Mode : Standard

Total number of virtual routers : 2

Interface Ten-GigabitEthernet3/1/2

VRID : 1 Adver Timer : 100

Admin Status : Up State : Master

Config Pri : 110 Running Pri : 110

Preempt Mode : Yes Delay Time : 500

Auth Type : None

Virtual IP : 10.1.1.1

Virtual MAC : 0000-5e00-0101

Master IP : 10.1.1.101

VRRP Track Information:

Track Object : 1 State : Positive Pri Reduced : 20

Interface Ten-GigabitEthernet3/1/3

VRID : 2 Adver Timer : 100

Admin Status : Up State : Backup

Config Pri : 100 Running Pri : 100

Preempt Mode : Yes Delay Time : 500

Become Master : 3550ms left

Auth Type : None

Virtual IP : 10.1.2.1

Master IP : 10.1.2.102

The output shows that Device A resumes its priority and becomes the master in VRRP group 1 again. Hosts in area B access the external network through Device A.

Configuration files

· Device A:

bfd echo-source-ip 10.10.10.10

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 1.1.1.1 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 10.1.1.101 255.255.255.0

vrrp vrid 1 virtual-ip 10.1.1.1

vrrp vrid 1 priority 110

vrrp vrid 1 preempt-mode delay 500

vrrp vrid 1 track 1 priority reduced 20

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 10.1.2.101 255.255.255.0

vrrp vrid 2 virtual-ip 10.1.2.1

vrrp vrid 2 preempt-mode delay 500

interface Ten-GigabitEthernet3/1/4

port link-mode route

ip address 192.168.2.101 255.255.255.0

track 1 bfd echo interface Ten-GigabitEthernet3/1/1 remote ip 1.1.1.2 local ip 1.1.1.1

· Device B:

bfd echo-source-ip 11.11.11.11

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 1.1.2.1 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 10.1.1.102 255.255.255.0

vrrp vrid 1 virtual-ip 10.1.1.1

vrrp vrid 1 preempt-mode delay 500

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 10.1.2.102 255.255.255.0

vrrp vrid 2 virtual-ip 10.1.2.1

vrrp vrid 2 priority 110

vrrp vrid 2 preempt-mode delay 500

vrrp vrid 2 track 1 priority reduced 20

interface Ten-GigabitEthernet3/1/4

port link-mode route

ip address 192.168.2.102 255.255.255.0

track 1 bfd echo interface Ten-GigabitEthernet3/1/1 remote ip 1.1.2.2 local ip 1.1.2.1

· Device E:

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 1.1.1.2 255.255.255.0

ip route-static 10.1.1.0 255.255.255.0 1.1.1.1

ip route-static 10.1.2.0 255.255.255.0 1.1.1.1

· Device F:

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 1.1.2.2 255.255.255.0

ip route-static 10.1.1.0 255.255.255.0 1.1.2.1

ip route-static 10.1.2.0 255.255.255.0 1.1.2.1

Example: Configuring BFD for static routing

Network configuration

As shown in Figure 2:

· Device A has two paths to reach Device B: one over a Layer 2 switch, and the other over Device C.

· A Layer 2 switch connects Device A and Device B.

Because Device B does not support BFD, enable BFD echo packet mode on Device A. When the link between Device B and the Layer 2 switch fails, Device A switches the path over Device C to reach Device B.

Figure 2 Network diagram

Table 1 Interface and IP address assignment

Device	Interface	IP address
Device A	XGE3/1/1	192.168.10.101/24
Device A	XGE3/1/2	192.168.20.101/24
Device A	XGE3/1/3	192.168.40.101/24
Device B	XGE3/1/1	192.168.10.102/24
Device B	XGE3/1/2	192.168.30.101/24
Device B	XGE3/1/3	192.168.50.101/24
Device C	XGE3/1/1	192.168.20.102/24
Device C	XGE3/1/2	192.168.30.102/24

Restrictions and guidelines

When you configure BFD for static routing, follow these restrictions and guidelines:

· For an SR8802-X-S router: If the router is not installed with a CSPEX-1404S or CSPEX-1504S card, the minimum interval for receiving echo packets cannot be smaller than 1000 milliseconds. If the router is installed with a CSPEX-1404S or CSPEX-1504S card, the minimum interval for receiving echo packets cannot be smaller than 100 milliseconds.

· For an SR8803-X-S router: If the router is not installed with the SR07SRPUC1 MPU, the minimum interval for receiving echo packets cannot be smaller than 100 milliseconds. If the router is installed with the SR07SRPUC1 MPU, the minimum interval for receiving echo packets cannot be smaller than 1000 milliseconds.

· For an SR8806-X-S or SR8810-X-S router: The minimum interval for receiving echo packets cannot be smaller than 100 milliseconds.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ip address 192.168.10.101 24

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring static routes

1. Configure Device A:

# Configure two static routes with the same destination network 192.168.50.0/24 and different preferences. Configure the BFD echo packet mode for the preferred static route (Device A –> L2 Switch–> Device B).

[DeviceA] ip route-static 192.168.50.0 24 ten-gigabitethernet 3/1/1 192.168.10.102 bfd echo-packet

[DeviceA] ip route-static 192.168.50.0 24 ten-gigabitethernet 3/1/1 192.168.20.102 preference 65

2. Configure Device B:

# Configure two static routes with the same destination network 192.168.40.0/24 and different preferences. Configure the BFD echo packet mode for the preferred static route (Device B –> L2 Switch–> Device A).

[DeviceB] ip route-static 192.168.40.0 24 ten-gigabitethernet 3/1/1 192.168.10.101

[DeviceB] ip route-static 192.168.40.0 24 ten-gigabitethernet 3/1/2 192.168.30.102 preference 65

3. Configure Device C:

# Configure static routes with destination networks 192.168.40.0/24 and 192.168.50.0/24.

[DeviceC] ip route-static 192.168.40.0 24 ten-gigabitethernet 3/1/1 192.168.20.101

[DeviceC] ip route-static 192.168.50.0 24 ten-gigabitethernet 3/1/2 192.168.30.101

Configuring BFD parameters on Device A

# Configure the source IP address for BFD echo packets.

[DeviceA] bfd echo-source-ip 10.10.10.10

# Configure the minimum interval for receiving BFD echo packets and the single-hop detection time multiplier.

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] bfd min-echo-receive-interval 100

[DeviceA-Ten-GigabitEthernet3/1/1] bfd detect-multiplier 3

[DeviceA-Ten-GigabitEthernet3/1/1] quit

Verifying the configuration

1. Verify the configuration when Device A and Device B and the link between them are operating correctly:

# Display static route information on Device A.

[DeviceA] display ip routing-table protocol static

Summary Count : 1

Static Routing table Status : <Active>

Summary Count : 1

Destination/Mask Proto Pre Cost NextHop Interface

192.168.50.0/24 Static 60 0 192.168.10.102 XGE3/1/1

Static Routing table Status : <Inactive>

Summary Count : 0

The output shows that Device A communicates with Device B through the Layer 2 switch.

# Display BFD session information on Device A.

[DeviceA] display bfd session

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Echo Mode:

LD/RD SourceAddr DestAddr State Holdtime Interface

67 192.168.10.101 192.168.10.102 Up 300ms XGE3/1/1

The output shows that a BFD session has been established.

2. Verify the configuration when the link between Device B and the Layer 2 switch is faulty:

# Display static route information on Device A.

[DeviceA] display ip routing-table protocol static

Summary Count : 1

Static Routing table Status : <Active>

Summary Count : 1

Destination/Mask Proto Pre Cost NextHop Interface

192.168.50.0/24 Static 65 0 192.168.20.102 XGE3/1/2

Static Routing table Status : <Inactive>

Summary Count : 0

The output shows that Device A communicates with Device B through Device C.

Configuration files

· Device A:

bfd echo-source-ip 10.10.10.10

bfd min-echo-receive-interval 100

bfd detect-multiplier 3

interface Ten-GigabitEthernet3/1/1

ip address 192.168.10.101 255.255.255.0

interface Ten-GigabitEthernet3/1/2

ip address 192.168.20.101 255.255.255.0

interface Ten-GigabitEthernet3/1/3

ip address 192.168.40.101 255.255.255.0

ip route-static 192.168.50.0 24 ten-gigabitethernet 3/1/1 192.168.10.102 bfd echo-packet

ip route-static 192.168.50.0 24 ten-gigabitethernet 3/1/2 192.168.20.102 preference 65

· Device B:

interface Ten-GigabitEthernet3/1/1

ip address 192.168.10.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

ip address 192.168.30.101 255.255.255.0

interface Ten-GigabitEthernet3/1/3

ip address 192.168.50.101 255.255.255.0

ip route-static 192.168.40.0 24 ten-gigabitethernet 3/1/1 192.168.10.101

ip route-static 192.168.40.0 24 ten-gigabitethernet 3/1/2 192.168.30.102 preference 65

· Device C:

interface Ten-GigabitEthernet3/1/1

ip address 192.168.20.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

ip address 192.168.30.102 255.255.255.0

ip route-static 192.168.40.0 24 ten-gigabitethernet 3/1/1 192.168.20.101

ip route-static 192.168.50.0 24 ten-gigabitethernet 3/1/2 192.168.30.101

Example: Configuring BFD for RIP

Network configuration

As shown in Figure 3, Device A, Device B, and Device C run RIP. Device A and Device C are connected through a Layer 2 switch.

Enable BFD echo packet mode on Device A (Device C does not support BFD) to monitor the path over the Layer 2 switch. When BFD detects a link failure, it notifies RIP to switch to the path over Device B.

Figure 3 Network diagram

Table 2 Interface and IP address assignment

Device	Interface	IP address
Device A	XGE3/1/1	10.1.0.101/24
Device A	XGE3/1/2	192.168.0.101/24
Device A	XGE3/1/3	120.1.1.1/24
Device B	XGE3/1/1	192.168.0.102/24
Device B	XGE3/1/2	13.1.1.101/24
Device C	XGE3/1/1	10.1.0.102/24
Device C	XGE3/1/2	13.1.1.102/24
Device C	XGE3/1/3	121.1.1.1/24

Restrictions and guidelines

When you configure BFD for RIP, follow these restrictions and guidelines:

· For an SR8806-X-S or SR8810-X-S router: The minimum interval for receiving echo packets cannot be smaller than 100 milliseconds.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ip address 10.1.0.101 24

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring RIP

1. Configure Device A:

# Configure basic RIP functions, import direct routes, and enable BFD for RIP.

<DeviceA> system-view

[DeviceA] rip 1

[DeviceA-rip-1] version 2

[DeviceA-rip-1] undo summary

[DeviceA-rip-1] network 10.1.0.0

[DeviceA-rip-1] network 192.168.0.0

[DeviceA-rip-1] import-route direct

[DeviceA-rip-1] quit

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] rip bfd enable

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure Device B:

# Configure basic RIP functions, and import direct routes.

<DeviceB> system-view

[DeviceB] rip 1

[DeviceB-rip-1] version 2

[DeviceB-rip-1] undo summary

[DeviceB-rip-1] network 192.168.0.0

[DeviceB-rip-1] network 13.1.1.0

[DeviceB-rip-1] import-route direct

[DeviceB-rip-1] quit

3. Configure Device C:

# Configure basic RIP functions, and import direct routes.

<DeviceC> system-view

[DeviceC] rip 1

[DeviceC-rip-1] version 2

[DeviceC-rip-1] undo summary

[DeviceC-rip-1] network 10.1.0.0

[DeviceC-rip-1] network 13.1.1.0

[DeviceC-rip-1] import-route direct

[DeviceC-rip-1] quit

Configuring BFD parameters on Device A

# Configure the source IP address for BFD echo packets.

[DeviceA] bfd echo-source-ip 11.11.11.11

# Configure the minimum interval for receiving BFD echo packets and the single-hop detection time multiplier.

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] bfd min-echo-receive-interval 100

[DeviceA-Ten-GigabitEthernet3/1/1] bfd detect-multiplier 3

[DeviceA-Ten-GigabitEthernet3/1/1] quit

Verifying the configuration

# Display BFD session information on Device A.

[DeviceA] display bfd session verbose

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Echo Mode:

Local Discr: 2049

Source IP: 10.1.0.101 Destination IP: 10.1.0.102

Session State: Up Interface: Ten-GigabitEthernet3/1/1

Hold Time: 300ms Act Tx Inter: 100ms

Min Rx Inter: 100ms Detect Inter: 300ms

Rx Count: 464 Tx Count: 465

Connect Type: Direct Running Up for: 00:00:46

Detect Mode: Async Slot: 0

Protocol: RIP

Diag Info: No Diagnostic

The output shows that a BFD session has been established and is up.

# Display information about the routes to network 121.1.1.0/24 on Device A.

<DeviceA> display ip routing-table 121.1.1.0 24 verbose

Summary Count : 1

Destination: 121.1.1.0/24

Protocol: RIP Process ID: 1

SubProtID: 0x1 Age: 04h20m37s

Cost: 1 Preference: 100

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NBRID: 0x26000002 LastAs: 0

AttrID: 0xffffffff Neighbor: 10.1.0.102

Flags: 0x1008c OrigNextHop: 10.1.0.102

Label: NULL RealNextHop: 10.1.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/1

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device A communicates with Device C through the Layer 2 switch.

# When the link between Device C and the Layer 2 switch fails, view BFD log information.

%Oct 9 18:42:17:650 2013 Device A BFD/5/BFD_CHANGE_FSM: -MDC=1;Sess[10.1.0.101/10.1.0.102, LD/RD:2049/2049, Interface: Ten-GigabitEthernet3/1/1, SessType:Echo, LinkType:INET] , Sta: UP-> DOWN, Diag:1

The output shows that BFD can quickly detect the failure and notify RIP.

# Display information about the routes to network 121.1.1.0/24 on Device A.

<DeviceA> display ip routing-table 121.1.1.0 24 verbose

Summary Count : 1

Destination: 121.1.1.0/24

Protocol: RIP Process ID: 2

SubProtID: 0x1 Age: 04h20m37s

Cost: 2 Preference: 100

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NBRID: 0x26000002 LastAs: 0

AttrID: 0xffffffff Neighbor: 192.168.0.102

Flags: 0x1008c OrigNextHop: 192.168.0.102

Label: NULL RealNextHop: 192.168.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/2

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device A communicates with Device C through Device B.

Configuration files

· Device A:

bfd echo-source-ip 11.11.11.11

rip 1

undo summary

version 2

network 10.0.0.0

network 192.168.0.0

import-route direct

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.101 255.255.255.0

bfd min-transmit-interval 100

bfd min-receive-interval 100

bfd detect-multiplier 3

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 192.168.0.101 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 120.1.1.1 255.255.255.0

· Device B:

rip 1

undo summary

version 2

network 192.168.0.0

network 13.1.1.0

import-route direct

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 192.168.0.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.101 255.255.255.0

· Device C:

rip 1

undo summary

version 2

network 10.1.0.0

network 13.1.1.0

import-route direct

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.102 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 121.1.1.1 255.255.255.0

Example: Configuring BFD for OSPF

Network configuration

As shown in Figure 4, Device A, Device B, and Device C run OSPF. Device A and Device C are connected through a Layer 2 switch.

Enable BFD control packet mode on Device A and Device C to monitor the path over the Layer 2 switch. When BFD detects a link failure, it notifies OSPF to switch to the path over Device B.

Figure 4 Network diagram

Table 3 Interface and IP address assignment

Device	Interface	IP address
Device A	XGE3/1/1	10.1.0.101/24
Device A	XGE3/1/2	192.168.0.101/24
Device A	XGE3/1/3	120.1.1.1/24
Device B	XGE3/1/1	192.168.0.102/24
Device B	XGE3/1/2	13.1.1.101/24
Device C	XGE3/1/1	10.1.0.102/24
Device C	XGE3/1/2	13.1.1.102/24
Device C	XGE3/1/3	121.1.1.1/24

Restrictions and guidelines

When you configure BFD for OSPF, follow these restrictions and guidelines:

· In BFD control packet mode, a minimum of one end must operate in active mode for a BFD session to be established.

· For an SR8806-X-S or SR8810-X-S router: The minimum interval for receiving echo packets cannot be smaller than 100 milliseconds.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ip address 10.1.0.101 24

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring OSPF

1. Configure Device A:

# Configure basic OSPF functions, and enable BFD for OSPF.

[DeviceA] ospf

[DeviceA-ospf-1] area 0

[DeviceA-ospf-1-area-0.0.0.0] network 10.1.0.0 0.0.0.255

[DeviceA-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255

[DeviceA-ospf-1-area-0.0.0.0] network 120.1.1.0 0.0.0.255

[DeviceA-ospf-1-area-0.0.0.0] quit

[DeviceA-ospf-1] quit

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ospf bfd enable

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure Device B:

# Configure basic OSPF functions.

[DeviceB] ospf

[DeviceB-ospf-1] area 0

[DeviceB-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255

[DeviceB-ospf-1-area-0.0.0.0] network 13.1.1.0 0.0.0.255

[DeviceB-ospf-1-area-0.0.0.0] quit

[DeviceB-ospf-1] quit

3. Configure Device C:

# Configure basic OSPF functions, and enable BFD for OSPF.

[DeviceC] ospf

[DeviceC-ospf-1] area 0

[DeviceC-ospf-1-area-0.0.0.0] network 10.1.0.0 0.0.0.255

[DeviceC-ospf-1-area-0.0.0.0] network 13.1.1.0 0.0.0.255

[DeviceC-ospf-1-area-0.0.0.0] network 121.1.1.0 0.0.0.255

[DeviceC-ospf-1-area-0.0.0.0] quit

[DeviceC-ospf-1] quit

[DeviceC] interface ten-gigabitethernet 3/1/1

[DeviceC-Ten-GigabitEthernet3/1/1] ospf bfd enable

[DeviceC-Ten-GigabitEthernet3/1/1] quit

Configuring BFD parameters

1. Configure Device A:

# Configure the session establishment mode as active (this is the default mode).

[DeviceA] bfd session init-mode active

# Configure the minimum interval for sending and receiving single-hop BFD control packets and the single-hop detection time multiplier.

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] bfd min-transmit-interval 100

[DeviceA-Ten-GigabitEthernet3/1/1] bfd min-receive-interval 100

[DeviceA-Ten-GigabitEthernet3/1/1] bfd detect-multiplier 3

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure Device C:

# Configure the session establishment mode as active (this is the default mode).

[DeviceC] bfd session init-mode active

# Configure the minimum interval for sending and receiving single-hop BFD control packets and the single-hop detection time multiplier.

[DeviceC] interface ten-gigabitethernet 3/1/1

[DeviceC-Ten-GigabitEthernet3/1/1] bfd min-transmit-interval 100

[DeviceC-Ten-GigabitEthernet3/1/1] bfd min-receive-interval 100

[DeviceC-Ten-GigabitEthernet3/1/1] bfd detect-multiplier 3

[DeviceC-Ten-GigabitEthernet3/1/1] quit

Verifying the configuration

# Ping host C (connected to Device C) from host A (connected to Device A) to verify the connectivity.

<host A> ping 121.1.1.2

PING 121.1.1.2 (121.1.1.2): 56 data bytes

56 bytes from 121.1.1.2: seq=0 ttl=128 time=22.43 ms

56 bytes from 121.1.1.2: seq=1 ttl=128 time=7.17 ms

56 bytes from 121.1.1.2: seq=2 ttl=128 time=8.91 ms

56 bytes from 121.1.1.2: seq=3 ttl=128 time=7.45 ms

56 bytes from 121.1.1.2: seq=4 ttl=128 time=9.11 ms

--- 121.1.1.2 ping statistics ---

5 packets transmitted, 5 packets received, 0% packet loss

round-trip min/avg/max = 7.17/11.01/22.43 ms

The output shows that host C can be pinged successfully.

# Display detailed OSPF neighbor information on Device A.

[DeviceA] display ospf peer verbose

OSPF Process 1 with Router ID 2.2.2.2

Neighbors

Area 0.0.0.0 interface 10.1.0.101(Ten-GigabitEthernet3/1/1)'s neighbors

Router ID: 1.1.1.1 Address: 10.1.0.102 GR State: Normal

State: Full Mode: Nbr is Slave Priority: 1

DR: 10.1.0.101 BDR: 10.1.0.102 MTU: 0

Options is 0x42 (-|O|-|-|-|-|E|-)

Dead timer due in 39 sec

Neighbor is up for 00:09:01

Authentication Sequence: [ 0 ]

Neighbor state change count: 5

BFD status: Enabled(Control mode)

The output shows that Device A has established OSPF neighbor relationship with Device C.

# Display BFD session information on Device A and Device C.

[DeviceA] display bfd session verbose

Total session number: 1 Up session number: 1 Init mode: Active

IPv4 session working under Ctrl mode:

Local Discr: 10 Remote Discr: 1

Source IP: 10.1.0.101 Destination IP: 10.1.0.102

Session State: Up Interface: Ten-GigabitEthernet3/1/1

Min Trans Inter: 100ms Act Trans Inter: 100ms

Min Recv Inter: 100ms Act Detect Inter: 300ms

Rx Count: 3971 Tx Count: 3776

Connect Type: Direct Running Up for: 00:06:52

Hold Time: 300ms Auth mode: None

Detect Mode: Async Slot: 0

Protocol: OSPF

Diag Info: No Diagnostic

[DeviceC] display bfd session verbose

Total session number: 1 Up session number: 1 Init mode: Active

IPv4 session working under Ctrl mode:

Local Discr: 1 Remote Discr: 10

Source IP: 10.1.0.102 Destination IP: 10.1.0.101

Session State: Up Interface: Ten-GigabitEthernet3/1/1

Min Trans Inter: 100ms Act Trans Inter: 100ms

Min Recv Inter: 100ms Act Detect Inter: 300ms

Min Trans Inter: 100ms Act Trans Inter: 100ms

Min Recv Inter: 100ms Act Detect Inter: 100ms

Rx Count: 3 Tx Count: 3

Connect Type: Direct Running Up for: 00:06:52

Hold Time: 300ms Auth mode: None

Detect Mode: Async Slot: 0

Protocol: OSPF

Diag Info: No Diagnostic

The output shows that BFD sessions have been established and are up.

# Display information about the routes to network 121.1.1.0/24 on Device A.

<DeviceA> display ip routing-table 121.1.1.0 verbose

Summary Count : 1

Destination: 120.1.1.0/24

Protocol: OSPF Process ID: 1

SubProtID: 0x1 Age: 04h20m37s

Cost: 1 Preference: 10

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NBRID: 0x26000002 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x1008c OrigNextHop: 10.1.0.102

Label: NULL RealNextHop: 10.1.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/1

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device A communicates with Device C through the Layer 2 switch.

# When the link between Device C and the Layer 2 switch fails, view BFD log information.

%Apr 2 11:34:26:880 2014 DeviceA BFD/5/BFD_CHANGE_FSM: Sess[10.1.0.101/10.1.0.102,1026/1026, Ten-GigabitEthernet3/1/1,Ctrl] , Sta: UP-> DOWN, Diag: 5

%Apr 2 11:34:27:011 2014 DeviceA OSPF/5/OSPF_NBR_CHG: OSPF 1 Neighbor 10.1.0.102 Ten-GigabitEthernet3/1/1) from Full to Down.

The output shows that BFD can quickly detect the failure and notify OSPF.

# Display information about the routes to network 121.1.1.0/24 on Device A.

<DeviceA> display ip routing-table 121.1.1.0 verbose

Summary Count : 1

Destination: 121.1.1.0/24

Protocol: OSPF Process ID: 1

SubProtID: 0x1 Age: 04h20m37s

Cost: 2 Preference: 10

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NBRID: 0x26000002 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x1008c OrigNextHop: 192.168.0.102

Label: NULL RealNextHop: 192.168.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/2

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device A communicates with Device C through Device B.

Configuration files

· Device A:

ospf 1

area 0.0.0.0

network 10.1.0.0 0.0.0.255

network 120.1.1.0 0.0.0.255

network 192.168.0.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.101 255.255.255.0

ospf bfd enable

bfd min-transmit-interval 100

bfd min-receive-interval 100

bfd detect-multiplier 3

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 192.168.0.101 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 120.1.1.1 255.255.255.0

· Device B:

ospf 1

area 0.0.0.0

network 13.1.1.0 0.0.0.255

network 192.168.0.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 192.168.0.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.101 255.255.255.0

· Device C:

ospf 1

area 0.0.0.0

network 10.1.0.0 0.0.0.255

network 13.1.1.0 0.0.0.255

network 121.1.1.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.102 255.255.255.0

ospf bfd enable

bfd min-transmit-interval 100

bfd min-receive-interval 100

bfd detect-multiplier 3

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.102 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 121.1.1.1 255.255.255.0

Example: Configuring BFD for IS-IS

Network configuration

As shown in Figure 5, Device A, Device B, and Device C run IS-IS. Device A and Device C are connected through a Layer 2 switch.

Enable BFD control packet mode on Device A and Device C to monitor the path over the Layer 2 switch. When BFD detects a link failure, it notifies IS-IS to switch to the path over Device B.

Figure 5 Network diagram

Table 4 Interface and IP address assignment

Device	Interface	IP address
Device A	XGE3/1/1	10.1.0.101/24
Device A	XGE3/1/2	192.168.0.101/24
Device A	XGE3/1/3	120.1.1.1/24
Device B	XGE3/1/1	192.168.0.102/24
Device B	XGE3/1/2	13.1.1.101/24
Device C	XGE3/1/1	10.1.0.102/24
Device C	XGE3/1/2	13.1.1.102/24
Device C	XGE3/1/3	121.1.1.1/24

Restrictions and guidelines

When you configure BFD for IS-IS, follow these restrictions and guidelines:

· In BFD control packet mode, a minimum of one end must operate in active mode for a BFD session to be established.

· For an SR8806-X-S or SR8810-X-S router: The minimum interval for receiving echo packets cannot be smaller than 100 milliseconds.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ip address 10.1.0.101 24

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring IS-IS

1. Configure Device A:

# Configure basic IS-IS functions, and enable BFD for IS-IS.

[DeviceA] isis

[DeviceA-isis-1] network-entity 10.0000.0000.0001.00

[DeviceA-isis-1] quit

[DeviceA] interface ten-gigabitethernet 3/1/2

[DeviceA-Ten-GigabitEthernet3/1/2] isis enable

[DeviceA-Ten-GigabitEthernet3/1/2] quit

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] isis enable

[DeviceA-Ten-GigabitEthernet3/1/1] isis bfd enable

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure Device B:

# Configure basic IS-IS functions.

[DeviceB] isis

[DeviceB-isis-1] network-entity 10.0000.0000.0003.00

[DeviceB-isis-1] quit

[DeviceB] interface ten-gigabitethernet 3/1/1

[DeviceB-Ten-GigabitEthernet3/1/1] isis enable

[DeviceB-Ten-GigabitEthernet3/1/1] quit

[DeviceB] interface ten-gigabitethernet 3/1/2

[DeviceB-Ten-GigabitEthernet3/1/2] isis enable

[DeviceB-Ten-GigabitEthernet3/1/2] quit

3. Configure Device C:

# Configure basic IS-IS functions, and enable BFD for IS-IS.

[DeviceC] isis

[DeviceC-isis-1] network-entity 10.0000.0000.0002.00

[DeviceC-isis-1] quit

[DeviceC] interface ten-gigabitethernet 3/1/1

[DeviceC-Ten-GigabitEthernet3/1/1] isis enable

[DeviceC-Ten-GigabitEthernet3/1/1] isis bfd enable

[DeviceC-Ten-GigabitEthernet3/1/1] quit

[DeviceC] interface ten-gigabitethernet 3/1/2

[DeviceC-Ten-GigabitEthernet3/1/2] isis enable

[DeviceC-Ten-GigabitEthernet3/1/2] quit

Configuring BFD parameters

1. Configure Device A:

# Configure the session establishment mode as active (this is the default mode).

[DeviceA] bfd session init-mode active

# Configure the minimum interval for sending and receiving single-hop BFD control packets and the single-hop detection time multiplier.

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] bfd min-transmit-interval 100

[DeviceA-Ten-GigabitEthernet3/1/1] bfd min-receive-interval 100

[DeviceA-Ten-GigabitEthernet3/1/1] bfd detect-multiplier 3

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure Device C:

# Configure the session establishment mode as active (this is the default mode).

[DeviceC] bfd session init-mode active

# Configure the minimum interval for sending and receiving single-hop BFD control packets and the single-hop detection time multiplier.

[DeviceC] interface ten-gigabitethernet 3/1/1

[DeviceC-Ten-GigabitEthernet3/1/1] bfd min-transmit-interval 100

[DeviceC-Ten-GigabitEthernet3/1/1] bfd min-receive-interval 100

[DeviceC-Ten-GigabitEthernet3/1/1] bfd detect-multiplier 3

[DeviceC-Ten-GigabitEthernet3/1/1] quit

Verifying the configuration

# Display detailed IS-IS neighbor information on Device A.

[DeviceA] display isis peer verbose

Peer information for IS-IS(1)

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

System ID: 0000.0000.0002

Interface: Ten-GigabitEthernet3/1/1 Circuit Id: 0000.0000.0002.01

State: Up HoldTime: 6s Type: L1(L1L2) PRI: 64

Area address(es): 00

Peer IP address(es): 10.1.0.102

Peer local circuit ID: 1

Peer circuit SNPA address: ce9d-d91d-d100

Uptime: 00:01:19

Adj protocol: IPv4

Graceful Restart capable

Restarting signal: No

Suppress adjacency advertisement: No

Local topology:

Remote topology:

The output shows that Device A has established IS-IS neighbor relationship with Device C.

# Display BFD session information on Device A and Device C.

[DeviceA] display bfd session verbose

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Ctrl Mode:

Local Discr: 2049 Remote Discr: 2049

Source IP: 10.1.0.101 Destination IP: 10.1.0.102

Session State: Up Interface: Ten-GigabitEthernet3/1/1

Min Tx Inter: 100ms Act Tx Inter: 100ms

Min Rx Inter: 100ms Detect Inter: 300ms

Rx Count: 3 Tx Count: 3

Connect Type: Direct Running Up for: 00:06:09

Hold Time: 300ms Auth mode: None

Detect Mode: Async Slot: 0

Protocol: ISIS_BR_L1/ISIS_BR_L2

Diag Info: No Diagnostic

[DeviceC] display bfd session verbose

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Ctrl Mode:

Local Discr: 2049 Remote Discr: 2049

Source IP: 10.1.0.102 Destination IP: 10.1.0.101

Session State: Up Interface: Ten-GigabitEthernet3/1/1

Min Tx Inter: 100ms Act Tx Inter: 100ms

Min Rx Inter: 100ms Detect Inter: 300ms

Rx Count: 3 Tx Count: 3

Connect Type: Direct Running Up for: 00:07:10

Hold Time: 300ms Auth mode: None

Detect Mode: Async Slot: 0

Protocol: ISIS_BR_L1/ISIS_BR_L2

Diag Info: No Diagnostic

The output shows that BFD sessions have been established and are up.

# Display information about the routes to network 121.1.1.0/24 on Device A.

<DeviceA> display ip routing-table 121.1.1.0 verbose

Summary Count : 1

Destination: 121.1.1.0/24

Protocol: isis Process ID: 1

SubProtID: 0x1 Age: 04h20m37s

Cost: 20 Preference: 15

Tag: 0 State: Active Adv

OrigTblID: 0x2 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NBRID: 0x26000002 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x1008c OrigNextHop: 10.1.0.102

Label: NULL RealNextHop: 10.1.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/1

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device A communicates with Device C through the Layer 2 switch.

# When the link between Device C and the Layer 2 switch fails, view BFD log information.

%Oct 9 16:11:24:163 2013 DeviceC BFD/5/BFD_CHANGE_FSM: -MDC=1; Sess[10.1.0.102/10.1.0.101, LD/RD:2049/2049, Interface: Ten-GigabitEthernet3/1/1, SessType:Ctrl, LinkType:INET] , S

ta: UP-> DOWN, Diag: 1

%Oct 9 16:11:24:164 2013 DeviceC ISIS/5/ISIS_NBR_CHG: -MDC=1; IS-IS 1, Level-1 adj

acency 0000.0000.0001 (Ten-GigabitEthernet3/1/1), state change to: DOWN.

%Oct 9 16:11:24:164 2013 DeviceC ISIS/5/ISIS_NBR_CHG: -MDC=1; IS-IS 1, Level-2 adj

acency 0000.0000.0001 (Ten-GigabitEthernet3/1/1), state change to: DOWN.

The output shows that BFD can quickly detect the failure and notify IS-IS.

# Display information about the routes to network 121.1.1.0/24 on Device A.

<DeviceA> display ip routing-table 121.1.1.0 verbose

Summary Count : 1

Destination: 121.1.1.0/24

Protocol: OSPF Process ID: 1

SubProtID: 0x1 Age: 04h20m37s

Cost: 21 Preference: 10

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NBRID: 0x26000002 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x1008c OrigNextHop: 192.168.0.102

Label: NULL RealNextHop: 192.168.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/2

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device A communicates with Device C through Device B.

Configuration files

· Device A:

isis 1

network-entity 10.0000.0000.0001.00

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.101 255.255.255.0

isis enable 1

isis bfd enable

bfd min-transmit-interval 100

bfd min-receive-interval 100

bfd detect-multiplier 3

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 192.168.0.101 255.255.255.0

isis enable 1

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 120.1.1.1 255.255.255.0

· Device B:

isis 1

network-entity 10.0000.0000.0003.00

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 192.168.0.102 255.255.255.0

isis enable 1

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.101 255.255.255.0

isis enable 1

· Device C:

isis 1

network-entity 10.0000.0000.0002.00

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.102 255.255.255.0

isis enable 1

isis bfd enable

bfd min-transmit-interval 100

bfd min-receive-interval 100

bfd detect-multiplier 3

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.102 255.255.255.0

isis enable 1

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 121.1.1.1 255.255.255.0

Example: Configuring BFD for BGP

Network configuration

As shown in Figure 6, the devices in AS 100 run OSPF to reach each other. There are two paths between Device B and Device D:

· Path A—Path over Device C.

· Path B—Path over Device E.

When both paths are available, BGP uses the path over Device C to forward traffic between Device A and Device F.

Enable BFD control packet mode on Device B and Device D to monitor the path over Device C. When BFD detects a link failure, it notifies BGP to switch to the path over Device E.

Figure 6 Network diagram

Table 5 Interface and IP address assignment

Device	Interface	IP address
Device A	XGE3/1/1	120.1.0.1/24
Device B	XGE3/1/1	10.1.0.101/24
Device B	XGE3/1/2	192.168.0.101/24
Device B	XGE3/1/3	120.1.0.2/24
Device C	XGE3/1/1	10.1.0.102/24
Device C	XGE3/1/2	10.2.0.102/24
Device D	XGE3/1/1	10.2.0.101/24
Device D	XGE3/1/2	13.1.1.101/24
Device D	XGE3/1/3	120.2.0.2/24
Device E	XGE3/1/1	192.168.0.102/24
Device E	XGE3/1/2	13.1.1.102/24
Device F	XGE3/1/1	120.2.0.1/24

Analysis

For Path A to become the primary path, use a routing policy to set a lower cost for Path A than Path B.

Restrictions and guidelines

In BFD control packet mode, a minimum of one end must operate in active mode for a BFD session to be established.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface ten-gigabitethernet 3/1/1

[DeviceA-Ten-GigabitEthernet3/1/1] ip address 120.1.0.1 24

[DeviceA-Ten-GigabitEthernet3/1/1] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring OSPF in AS 100

1. Configure Device B:

[DeviceB] ospf

[DeviceB-ospf-1] import-route direct

[DeviceB-ospf-1] area 0

[DeviceB-ospf-1-area-0.0.0.0] network 10.1.0.0 0.0.0.255

[DeviceB-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255

[DeviceB-ospf-1-area-0.0.0.0] quit

[DeviceB-ospf-1] quit

2. Configure Device C:

[DeviceC] ospf

[DeviceC-ospf-1] area 0

[DeviceC-ospf-1-area-0.0.0.0] network 10.1.0.0 0.0.0.255

[DeviceC-ospf-1-area-0.0.0.0] network 10.2.0.0 0.0.0.255

[DeviceC-ospf-1-area-0.0.0.0] quit

[DeviceC-ospf-1] quit

3. Configure Device D:

[DeviceD] ospf

[DeviceD-ospf-1] import-route direct

[DeviceD-ospf-1] area 0

[DeviceD-ospf-1-area-0.0.0.0] network 10.2.0.0 0.0.0.255

[DeviceD-ospf-1-area-0.0.0.0] network 13.1.1.0 0.0.0.255

[DeviceD-ospf-1-area-0.0.0.0] quit

[DeviceD-ospf-1] quit

4. Configure Device E:

[DeviceE] ospf

[DeviceE-ospf-1] area 0

[DeviceE-ospf-1-area-0.0.0.0] network 13.1.1.0 0.0.0.255

[DeviceE-ospf-1-area-0.0.0.0] network 192.168.0.0 0.0.0.255

[DeviceE-ospf-1-area-0.0.0.0] quit

[DeviceE-ospf-1] quit

Configuring BGP

1. Configure Device A:

# Enable BGP and set the local AS number to 200.

[DeviceA] bgp 200

[DeviceA-bgp-default] router-id 1.1.1.1

# Establish an EBGP connection with Device B.

[DeviceA-bgp-default] peer 120.1.0.2 as-number 100

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

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

# In BGP IPv4 unicast address family view, inject local network 120.1.0.0/24 to the BGP routing table.

[DeviceA-bgp-default-ipv4] network 120.1.0.0 255.255.255.0

# Enable BGP to exchange IPv4 unicast routing information with peer 120.1.0.2.

[DeviceA-bgp-default-ipv4] peer 120.1.0.2 enable

[DeviceA-bgp-default-ipv4] quit

2. Configure Device B:

# Enable BGP and set the local AS number to 100.

[DeviceB] bgp 100

[DeviceB-bgp-default] router-id 2.2.2.2

# Establish an EBGP connection with Device A.

[DeviceB-bgp-default] peer 120.1.0.1 as-number 200

# Establish IBGP connections with Device D.

[DeviceB-bgp-default] peer 10.2.0.101 as-number 100

[DeviceB-bgp-default] peer 13.1.1.101 as-number 100

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

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

# Enable BGP to exchange IPv4 unicast routing information with peer 10.2.0.101.

[DeviceB-bgp-default-ipv4] peer 10.2.0.101 enable

# In BGP IPv4 unicast address family view, specify the device as the next hop for routes sent to peer 10.2.0.101.

[DeviceB-bgp-default-ipv4] peer 10.2.0.101 next-hop-local

# Enable BGP to exchange IPv4 unicast routing information with peer 13.1.1.101.

[DeviceB-bgp-default-ipv4] peer 13.1.1.101 enable

# In BGP IPv4 unicast address family view, specify the device as the next hop for routes sent to peer 13.1.1.101.

[DeviceB-bgp-default-ipv4] peer 13.1.1.101 next-hop-local

# Enable BGP to exchange IPv4 unicast routing information with peer 120.1.0.1.

[DeviceB-bgp-default-ipv4] peer 120.1.0.1 enable

[DeviceB-bgp-default-ipv4] quit

3. Configure Device D:

# Enable BGP and set the local AS number to 100.

[DeviceD] bgp 100

[DeviceD-bgp-default] router-id 4.4.4.4

# Establish IBGP connections with Device B.

[DeviceD-bgp-default] peer 10.1.0.101 as-number 100

[DeviceD-bgp-default] peer 192.168.0.101 as-number 100

# Establish an EBGP connection with Device F.

[DeviceD-bgp-default] peer 120.2.0.1 as-number 300

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

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

# Enable BGP to exchange IPv4 unicast routing information with peer 10.1.0.101.

[DeviceD-bgp-default-ipv4] peer 10.1.0.101 enable

# In BGP IPv4 unicast address family view, specify the device as the next hop for routes sent to peer 10.1.0.101.

[DeviceD-bgp-default-ipv4] peer 10.1.0.101 next-hop-local

# Enable BGP to exchange IPv4 unicast routing information with peer 192.168.0.101.

[DeviceD-bgp-default-ipv4] peer 192.168.0.101 enable

# In BGP IPv4 unicast address family view, specify the device as the next hop for routes sent to peer 192.168.0.101.

[DeviceD-bgp-default-ipv4] peer 192.168.0.101 next-hop-local

# Enable BGP to exchange IPv4 unicast routing information with peer 120.2.0.1.

[DeviceD-bgp-default-ipv4] peer 120.2.0.1 enable

[DeviceD-bgp-default-ipv4] quit

4. Configure Device F:

# Enable BGP and set the local AS number to 300.

[DeviceF] bgp 300

[DeviceF-bgp-default] router-id 6.6.6.6

# Establish an EBGP connection with Device D.

[DeviceF-bgp-default] peer 120.2.0.2 as-number 100

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

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

# In BGP IPv4 unicast address family view, inject local network 120.2.0.0/24 to the BGP routing table.

[DeviceF-bgp-default-ipv4] network 120.2.0.0 255.255.255.0

# Enable BGP to exchange IPv4 unicast routing information with peer 120.2.0.2.

[DeviceF-bgp-default-ipv4] peer 120.2.0.2 enable

[DeviceF-bgp-default-ipv4] quit

Configuring routing policies

1. Configure Device B:

# Create ACL 2000 to permit packets sourced from 120.1.0.0/24.

[DeviceB] acl basic 2000

[DeviceB-acl-ipv4-basic-2000] rule permit source 120.1.0.0 0.0.0.255

[DeviceB-acl-ipv4-basic-2000] quit

# Set a local preference of 200 for routes advertised to peer 10.2.0.101, and set the preference for IBGP routes to 100.

[DeviceB] route-policy local-pre permit node 10

[DeviceB-route-policy-local-pre-10] if-match ip address acl 2000

[DeviceB-route-policy-local-pre-10] apply local-preference 200

[DeviceB-route-policy-local-pre-10] quit

[DeviceB] bgp 100

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

[DeviceB-bgp-default-ipv4] peer 10.2.0.101 route-policy local-pre export

[DeviceB-bgp-default-ipv4] preference 255 100 130

[DeviceB-bgp-default-ipv4] quit

[DeviceB-bgp-default] quit

2. Configure Device D:

# Create ACL 2000 to permit packets sourced from 120.2.0.0/24.

[DeviceD] acl basic 2000

[DeviceD-acl-ipv4-basic-2000] rule permit source 120.2.0.0 0.0.0.255

[DeviceD-acl-ipv4-basic-2000] quit

# Set a local preference of 200 for routes learned from peer 10.1.0.101, and configure the preference for IBGP routes as 100.

[DeviceD] route-policy local-pre permit node 10

[DeviceD-route-policy-local-pre-10] if-match ip address acl 2000

[DeviceD-route-policy-local-pre-10] apply local-preference 200

[DeviceD-route-policy-local-pre-10] quit

[DeviceD] bgp 100

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

[DeviceD-bgp-default-ipv4] peer 10.1.0.101 route-policy local-pre export

[DeviceD-bgp-default-ipv4] preference 255 100 130

[DeviceD-bgp-default-ipv4] quit

[DeviceD-bgp-default] quit

Configuring BFD

1. Configure Device B:

# Enable BFD for the link to BGP peer 10.2.0.101.

[DeviceB] bgp 100

[DeviceB-bgp-default] peer 10.2.0.101 bfd

[DeviceB-bgp-default] quit

2. Configure Device D:

# Enable BFD for the link to BGP peer 10.1.0.101.

[DeviceD] bgp 100

[DeviceD-bgp-default] peer 10.1.0.101 bfd

[DeviceD-bgp-default] quit

Verifying the configuration

# Ping Device F from Device A to verify the connectivity.

[DeviceA] ping 120.2.0.1

Ping 120.2.0.1 (120.2.0.1): 56 data bytes, press CTRL_C to break

56 bytes from 120.2.0.1: icmp_seq=0 ttl=252 time=1.189 ms

56 bytes from 120.2.0.1: icmp_seq=1 ttl=252 time=1.095 ms

56 bytes from 120.2.0.1: icmp_seq=2 ttl=252 time=1.086 ms

56 bytes from 120.2.0.1: icmp_seq=3 ttl=252 time=1.097 ms

56 bytes from 120.2.0.1: icmp_seq=4 ttl=252 time=1.089 ms

--- Ping statistics for 120.2.0.1 ---

5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss

round-trip min/avg/max/std-dev = 1.086/1.111/1.189/0.039 ms

The output shows that Device F can be pinged successfully.

# Display BGP peer information on Device B.

[DeviceB] display bgp peer ipv4

BGP local router ID: 2.2.2.2

Local AS number: 100

Total number of peers: 3 Peers in established state: 3

Peer AS MsgRcvd MsgSent OutQ PrefRcv Up/Down State

10.2.0.101 100 6 4 0 1 00:00:56 Established

13.1.1.101 100 6 5 0 1 00:00:56 Established

120.1.0.1 200 6 5 0 1 00:00:56 Established

The output shows the following information:

· Two IBGP connections have been established between Device B and Device D.

· An EBGP connection has been established between Device B and Device A.

# Display detailed BFD session information on Device B.

[DeviceB] display bfd session verbose

Total Session Num: 1 Up Session Num: 0 Init Mode: Active

IPv4 Session Working Under Ctrl Mode:

Local Discr: 2049 Remote Discr: 0

Source IP: 10.1.0.101 Destination IP: 10.2.0.101

Session State: UP Interface: N/A

Min Tx Inter: 1000400ms Act Tx Inter: 1000400ms

Min Rx Inter: 1000400ms Detect Inter: 50002000ms

Rx Count: 0 Tx Count: 910

Connect Type: Indirect Running Up for: 00:00:00

Hold Time: 0ms Auth mode: None

Detect Mode: Async Slot: 0

Protocol: BGP

Diag Info: No Diagnostic

The output shows that a BFD session has been established and is up.

# Display information about the routes to network 120.2.0.0/24 on Device B.

[DeviceB] display ip routing-table 120.2.0.0 24 verbose

Summary Count : 3

Destination: 120.2.0.0/24

Protocol: BGP Process ID: 0

SubProtID: 0x1 Age: 00h24m48s

Cost: 0 Preference: 100

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 300

NibID: 0x15000001 LastAs: 300

AttrID: 0x1 Neighbor: 10.2.0.101

Flags: 0x10060 OrigNextHop: 10.2.0.101

Label: NULL RealNextHop: 10.1.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/1

BkTunnel ID: Invalid BkInterface: N/A

Destination: 120.2.0.0/24

Protocol: OSPF Process ID: 1

SubProtID: 0x8 Age: 00h26m19s

Cost: 1 Preference: 150

Tag: 1 State: Inactive Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NibID: 0x13000005 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x41 OrigNextHop: 10.1.0.102

Label: NULL RealNextHop: 10.1.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/1

BkTunnel ID: Invalid BkInterface: N/A

Destination: 120.2.0.0/24

Protocol: OSPF Process ID: 1

SubProtID: 0x8 Age: 00h26m19s

Cost: 1 Preference: 150

Tag: 1 State: Inactive Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NibID: 0x13000003 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x41 OrigNextHop: 192.168.0.102

Label: NULL RealNextHop: 192.168.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/2

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device B communicates with Device D through path over Device C.

# When the path over Device C fails, ping Device F from Device A.

<DeviceA> ping 120.2.0.1

Ping 120.1.0.1 (120.2.0.1): 56 data bytes, press CTRL_C to break

56 bytes from 120.2.0.1: icmp_seq=0 ttl=252 time=0.680 ms

56 bytes from 120.2.0.1: icmp_seq=1 ttl=252 time=0.295 ms

56 bytes from 120.2.0.1: icmp_seq=2 ttl=252 time=0.423 ms

56 bytes from 120.2.0.1: icmp_seq=3 ttl=252 time=0.464 ms

56 bytes from 120.2.0.1: icmp_seq=4 ttl=252 time=0.445 ms

--- Ping statistics for 120.2.0.1 ---

5 packets transmitted, 5 packets received, 0.0% packet loss

round-trip min/avg/max/std-dev = 0.295/0.461/0.680/0.124 ms

The output shows that Device F can be pinged successfully.

# Display information about the routes to network 120.2.0.0/24 on Device B.

<DeviceB> display ip routing-table 120.2.0.0 24 verbose

Summary Count : 2

Destination: 120.2.0.0/24

Protocol: BGP Process ID: 0

SubProtID: 0x1 Age: 00h00m18s

Cost: 0 Preference: 100

Tag: 0 State: Active Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 300

NibID: 0x15000001 LastAs: 300

AttrID: 0x1 Neighbor: 10.2.0.101

Flags: 0x10060 OrigNextHop: 10.2.0.101

Label: NULL RealNextHop: 192.168.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/2

BkTunnel ID: Invalid BkInterface: N/A

Destination: 120.2.0.0/24

Protocol: OSPF Process ID: 1

SubProtID: 0x8 Age: 00h00m18s

Cost: 1 Preference: 150

Tag: 1 State: Inactive Adv

OrigTblID: 0x0 OrigVrf: default-vrf

TableID: 0x2 OrigAs: 0

NibID: 0x13000001 LastAs: 0

AttrID: 0xffffffff Neighbor: 0.0.0.0

Flags: 0x41 OrigNextHop: 192.168.0.102

Label: NULL RealNextHop: 192.168.0.102

BkLabel: NULL BkNextHop: N/A

Tunnel ID: Invalid Interface: Ten-GigabitEthernet3/1/2

BkTunnel ID: Invalid BkInterface: N/A

The output shows that Device B communicates with Device D through path over Device E.

Configuration files

· Device A:

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 120.1.0.1 255.255.255.0

bgp 200

router-id 1.1.1.1

peer 120.1.0.2 as-number 200

address-family ipv4 unicast

network 120.1.0.0 255.255.255.0

peer 120.1.0.2 enable

· Device B:

ospf 1

import-route direct

area 0.0.0.0

network 10.1.0.0 0.0.0.255

network 192.168.0.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.101 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 192.168.0.101 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 120.1.0.2 255.255.255.0

bgp 100

router-id 2.2.2.2

peer 10.2.0.101 as-number 100

peer 10.2.0.101 bfd

peer 13.1.1.101 as-number 100

peer 120.1.0.1 as-number 200

address-family ipv4 unicast

preference 255 100 130

peer 10.2.0.101 enable

peer 10.2.0.101 next-hop-local

peer 10.2.0.101 route-policy local-pre export

peer 13.1.1.101 enable

peer 13.1.1.101 next-hop-local

peer 120.1.0.1 enable

route-policy local-pre permit node 10

if-match ip address acl 2000

apply local-preference 200

acl basic 2000

rule 0 permit source 120.1.0.0 0.0.0.255

· Device C:

ospf 1

area 0.0.0.0

network 10.1.0.0 0.0.0.255

network 10.2.0.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.1.0.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 10.2.0.102 255.255.255.0

· Device D:

ospf 1

import-route direct

area 0.0.0.0

network 10.2.0.0 0.0.0.255

network 13.1.1.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 10.2.0.101 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.101 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 120.1.0.2 255.255.255.0

bgp 100

router-id 4.4.4.4

peer 10.1.0.101 as-number 100

peer 10.1.0.101 bfd

peer 120.2.0.1 as-number 300

peer 192.168.0.101 as-number 100

address-family ipv4 unicast

preference 255 100 130

peer 10.1.0.101 enable

peer 10.1.0.101 next-hop-local

peer 10.1.0.101 route-policy local-pre export

peer 192.168.0.101 enable

peer 192.168.0.101 next-hop-local

peer 120.2.0.1 enable

acl basic 2000

rule 0 permit source 120.2.0.0 0.0.0.255

· Device E:

ospf 1

area 0.0.0.0

network 13.1.1.0 0.0.0.255

network 192.168.0.0 0.0.0.255

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 192.168.0.102 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 13.1.1.102 255.255.255.0

· Device F:

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 120.2.0.1 255.255.255.0

bgp 300

router-id 6.6.6.6

peer 120.2.0.2 as-number 100

address-family ipv4 unicast

network 120.2.0.0 255.255.255.0

peer 120.2.0.2 enable

Example: Configuring BFD for PBR

Network configuration

As shown in Figure 7, Device A has two paths to reach Device C:

· Link A.

· Link B.

Configure PBR to enable Device A to forward traffic with source IP address 40.0.0.2 over Link B.

Enable BFD echo packet mode on Device A (Device C does not support BFD) to monitor Link B. When BFD detects a link failure, Device A switches the path to Link A.

Figure 7 Network diagram

Restrictions and guidelines

When you configure BFD for PBR, follow these restrictions and guidelines:

· For an SR8806-X-S or SR8810-X-S router: The minimum interval for receiving echo packets cannot be smaller than 100 milliseconds.

Procedures

Configuring interface IP addresses

1. Configure Device A:

<DeviceA> system-view

[DeviceA] interface Ten-GigabitEthernet 3/1/2

[DeviceA-Ten-GigabitEthernet3/1/2] ip address 40.0.0.1 24

[DeviceA-Ten-GigabitEthernet3/1/2] quit

2. Configure other devices in the same way Device A is configured. (Details not shown.)

Configuring static routes

1. Configure Device A:

# Configure a static route to reach network 50.0.0.0.

[DeviceA] ip route-static 50.0.0.0 24 ten-gigabitethernet 3/1/1 13.13.13.2

2. Configure Device B:

# Configure a static route to reach network 50.0.0.0.

[DeviceB] ip route-static 50.0.0.0 24 ten-gigabitethernet 3/1/2 24.24.24.4

Configuring routing policies on Device A

# Create ACL 3010 to permit packets sourced from 40.0.0.2.

[DeviceA] acl advanced 3010

[DeviceA-acl-ipv4-adv-3010] rule 0 permit ip source 40.0.0.2 0

[DeviceA-acl-ipv4-adv-3010] quit

# Create routing policy aaa to set next hop 12.12.12.2 for packets matching ACL 3010, and associate the next hop with track entry 11.

[DeviceA] policy-based-route aaa permit node 5

[DeviceA-pbr-aaa-5] if-match acl 3010

[DeviceA-pbr-aaa-5] apply next-hop 12.12.12.2 track 11

[DeviceA-pbr-aaa-5] quit

# Apply routing policy aaa to Ten-GigabitEthernet 3/1/2.

[DeviceA] interface ten-gigabitEthernet 3/1/2

[DeviceA-Ten-GigabitEthernet3/1/2] ip policy-based-route aaa

[DeviceA-Ten-GigabitEthernet3/1/2] quit

Configuring BFD parameters on Device A

# Configure the source IP address for BFD echo packets.

[DeviceA] bfd echo-source-ip 3.3.3.3

# Configure the minimum interval for receiving BFD echo packets and the single-hop detection time multiplier, and associate track entry 11 with BFD.

[DeviceA] interface ten-gigabitethernet 3/1/3

[DeviceA-Ten-GigabitEthernet3/1/3] bfd min-echo-receive-interval 100

[DeviceA-Ten-GigabitEthernet3/1/3] bfd detect-multiplier 3

[DeviceA-Ten-GigabitEthernet3/1/3] quit

[DeviceA] track 11 bfd echo interface ten-gigabitethernet 3/1/3 remote ip 12.12.12.2 local ip 12.12.12.1

Verifying the configuration

# Display outbound traffic statistics for all interfaces on Device A.

<DeviceA> reset counters interface

<DeviceA> display counters outbound interface

Interface Total (pkts) Broadcast (pkts) Multicast (pkts) Err (pkts)

XGE3/1/1 0 0 0 0

XGE3/1/2 0 0 0 0

XGE3/1/3 585414 0 0 0

XGE3/1/4 0 0 0 0

XGE3/1/5 0 0 0 0

XGE3/1/6 0 0 0 0

The output shows that the traffic sourced from 40.0.0.0 is forwarded through Ten-GigabitEthernet 3/1/3 (Link B).

# Display BFD session information on Device A.

[DeviceA] display bfd session verbose

Total Session Num: 1 Up Session Num: 1 Init Mode: Active

IPv4 Session Working Under Echo Mode:

Local Discr: 2049

Source IP: 12.12.12.1 Destination IP: 12.12.12.2

Session State: Up Interface: Ten-GigabitEthernet3/1/3

Min Tx Inter: 100ms Act Tx Inter: 100ms

Min Rx Inter: 100ms Detect Inter: 300ms

Rx Count: 128234 Tx Count: 371950

Connect Type: Direct Running Up for: 00:01:04

Detect Mode: Async Chassis/Slot: 1/0

Protocol: TRACK

Diag Info: No Diagnostic

The output shows that a BFD session has been established and is up.

# When the link between Device A and Device B fails, view BFD log information.

%Dec 10 16:39:46:210 2013 DeviceA BFD/5/BFD_CHANGE_FSM: -MDC=1; Sess[12.12.12.1/

12.12.12.2, LD/RD:2049/2049, Interface: Ten-GigabitEthernet3/1/3, SessType:Echo, LinkType:INET] , S

ta: UP-> DOWN, Diag: 1

%Dec 10 16:39:47:342 2013 DeviceA IFNET/3/PHY_UPDOWN: -MDC=1; Ten-GigabitEthernet3/1/3 link status is down.

%Dec 10 16:39:47:343 2013 DeviceA IFNET/5/LINK_UPDOWN: -MDC=1; Line protocol on

the interface Ten-GigabitEthernet3/1/3 is down.

%Dec 10 16:39:47:343 2013 DeviceA IFNET/3/PHY_UPDOWN: -MDC=1; Ten-GigabitEthernet3/1/3

link status is down.

The output shows that the BFD session is down.

# Clear the interface statistics, and display outbound traffic statistics for all interfaces on Device A again.

<DeviceA> reset counters interface

<DeviceA> display counters outbound interface

Interface Total (pkts) Broadcast (pkts) Multicast (pkts) Err (pkts)

XGE3/1/1 863764 0 0 0

XGE3/1/2 0 0 0 0

XGE3/1/3 0 0 0 0

XGE3/1/4 0 0 0 0

XGE3/1/5 0 0 0 0

XGE3/1/6 0 0 0 0

The output shows that the traffic sourced from 40.0.0.0 is forwarded through Ten-GigabitEthernet 3/1/1 (Link A).

Configuration files

· Device A:

bfd echo-source-ip 3.3.3.3

policy-based-route aaa permit node 5

if-match acl 3010

apply next-hop 12.12.12.2 track 11

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 13.13.13.1 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 40.0.0.1 255.255.255.0

ip policy-based-route aaa

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 12.12.12.1 255.255.255.0

bfd min-echo-receive-interval 10

bfd detect-multiplier 3

ip route-static 50.0.0.0 24 Ten-GigabitEthernet3/1/1 13.13.13.2

ip local policy-based-route aaa

acl advanced 3010

rule 0 permit ip source 40.0.0.2 0

track 11 bfd echo interface Ten-GigabitEthernet3/1/3 remote ip 12.12.12.2 local ip 12.12.12.1

· Device B:

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 12.12.12.2 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 24.24.24.2 255.255.255.0

ip route-static 50.0.0.0 24 Ten-GigabitEthernet3/1/2 24.24.24.4

· Device C:

interface Ten-GigabitEthernet3/1/1

port link-mode route

ip address 13.13.13.2 255.255.255.0

interface Ten-GigabitEthernet3/1/2

port link-mode route

ip address 50.0.0.1 255.255.255.0

interface Ten-GigabitEthernet3/1/3

port link-mode route

ip address 24.24.24.4 255.255.255.0

01-Typical configuration example

Prerequisites

General restrictions and guidelines

Verifying the configuration

Example: Configuring BFD for static routing

Example: Configuring BFD for RIP

Example: Configuring BFD for OSPF

Example: Configuring BFD for IS-IS

Example: Configuring BFD for BGP

Example: Configuring BFD for PBR

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