Maipu Administration Guide

Configure IS-IS to Coordinate with BFD

Network Requirements

Configure the BFD coordination between devices. When the main line is faulty, services can be quickly switched to the backup line.
Device1, Device2, and Device3 are the Level-2 routers in the same area, Area 10. Configure the BFD on Device1 and Device3 to initiate a session. When the line between Device1 and Device3 disconnects, Device1 can perform switching quickly and learn the 10.1.1.1/24 routing from Device2.

Network Topology

Networking of the IS-IS coordinating with the BFD

Figure 9–6 Networking of the IS-IS coordinating with the BFD

Configuration Steps

Step 1: Configure the IP address of the interfaces. (Omitted)

Step 2: Configure the IS-IS and enable the process on the interface.

#Configure the IS-IS process as 100, area number as 10, and type as Level-2 and enable the process on the interface on Device1.

Device1#configure terminal
Device1(config)#router isis 100
Device1(config-isis)#net 10.0000.0000.0001.00
Device1(config-isis)#is-type level-2
Device1(config-isis)#metric-style wide
Device1(config-isis)#exit
Device1(config)#interface vlan2
Device1(config-if-vlan2)#ip router isis 100
Device1(config-if- vlan2)#exit
Device1(config)#interface vlan4
Device1(config-if-vlan4)#ip router isis 100
Device1(config-if-vlan4)#exit

#Configure the IS-IS process as 100, area number as 10, and type as Level-2 and enable the process on the interface on Device2.

Device2#configure terminal
Device2(config)#router isis 100
Device2(config-isis)#net 10.0000.0000.0002.00
Device2(config-isis)#is-type level-2
Device2(config-isis)#metric-style wide
Device2(config-isis)#exit
Device2(config)#interface vlan2
Device2(config-if-vlan2)#ip router isis 100
Device2(config-if-vlan2)#exit
Device2(config)#interface vlan3
Device2(config-if-vlan3)#ip router isis 100
Device2(config-if-vlan3)#exit

#Configure the IS-IS process as 100, area number as 10, and type as Level-2 and enable the process on the interface on Device3.

Device3#configure terminal
Device3(config)#router isis 100
Device3(config-isis)#net 10.0000.0000.0003.00
Device3(config-isis)#is-type level-2
Device3(config-isis)#metric-style wide
Device3(config-isis)#exit
Device3(config)#interface vlan2
Device3(config-if-vlan2)#ip router isis 100
Device3(config-if-vlan2)#exit
Device3(config)#interface vlan3
Device3(config-if-vlan3)#ip router isis 100
Device3(config-if-vlan3)#exit
Device3(config)#interface vlan4
Device3(config-if-vlan4)#ip router isis 100
Device3(config-if-vlan4)#exit

#View the routing information of Device1. Device1 preferentially chooses the routing 10.1.1.0/24 advertised by Device3.

Device1#show ip route  
Codes: C - connected, S - static, R - RIP, O - OSPF, OE-OSPF External, M - Management 
       D - Redirect, E - IRMP, EX - IRMP external, o - SNSP, B - BGP, i-IS-IS  
 
Gateway of last resort is not set 
 
i 10.1.1.0/24 [115/20] via 100.1.1.2, 00:00:15, vlan4 
C 100.1.1.0/24 is directly connected, 00:09:15, vlan4
C 127.0.0.0/8 is directly connected, 253:58:17, lo0 
C 200.1.1.0/24 is directly connected, 00:11:29, vlan2
i 210.1.1.0/24 [115/20] via 100.1.1.2, 00:00:15, vlan4 
               [115/20] via 200.1.1.2, 00:00:15, vlan2

Device1#show isis ipv4 route 
IS-IS Instance 100, VRF Kernel, IPv4 routes table (Counter 4):
L2 10.1.1.0/24, flags none, metric 20, from learned, installed 
     via 100.1.1.2, vlan4, neighbor 0000.0000.0003 
L2 100.1.1.0/24, flags none, metric 10, from network connected 
     via 0.0.0.0, vlan4 
L2 200.1.1.0/24, flags none, metric 10, from network connected 
     via 0.0.0.0, vlan2 
L2 210.1.1.0/24, flags none, metric 20, from learned, installed 
     via 100.1.1.2, vlan4, neighbor 0000.0000.0003 
     via 200.1.1.2, vlan2, neighbor 0000.0000.0002

Step 3: Configure the BFD.

#Enable the BFD on the interface of Device1.

Device1(config)#bfd fast-detect
Device1(config)#interface vlan4
Device1(config-if-vlan4)#isis bfd
Device1(config-if-vlan4)#exit

#Enable the BFD on the Device3 interface.

Device3(config)#bfd fast-detect
Device3(config)#interface vlan4
Device3(config-if-vlan4)#isis bfd
Device3(config-if-vlan4)#exit

#View the BFD information of Device1.

Device1#show bfd session  
OurAddr     NeighAddr    LD/RD  State Holddown   interface        
100.1.1.2	100.1.1.1    1/1    UP    5000       vlan4

Step 4: Check the result.

#When the line between Device1 and Device3 is faulty, the BFD quickly detects the fault and informs the fault to the IS-IS. The ISIS switches the routing to Device2 for communication. View the routing table of Device1.

Device1#show ip route    
Codes: C - connected, S - static, R - RIP, O - OSPF, OE-OSPF External, M - Management 
       D - Redirect, E - IRMP, EX - IRMP external, o - SNSP, B - BGP, i-IS-IS  
 
Gateway of last resort is not set 
 
i 10.1.1.0/24 [115/30] via 200.1.1.2, 00:00:14, vlan2 
C 127.0.0.0/8 is directly connected, 112:55:25, lo0 
C 200.1.1.0/24 is directly connected, 101:20:08, vlan2 
 
Device1#show isis ipv4 route  
IS-IS Instance 100, VRF Kernel, IPv4 routes table (Counter 2):
L2 10.1.1.0/24, flags none, metric 30, from l earned, installed 
     via 200.1.1.2, vlan2, neighbor 0000.0000.0003 
L2 200.1.1.0/24, flags none, metric 20, from network connected 
     via 0.0.0.0, vlan2

#It can be viewed that the data flow from Device1 to the 10.1.1.0/24 network segment priors to Device2.