IS-IS FRR configuration example

As shown in Figure 47, Switch A, Switch B, and Switch C belong to the same IS-IS routing domain. Configure IS-IS FRR so that when the Link A fails, traffic can be switched to Link B immediately.

1. Configure IP addresses and subnet masks for interfaces on the switches. (Details not shown.)

2. Configure IS-IS on the switches to make sure Switch A, Switch B, and Switch C can communicate with each other at Layer 3. (Details not shown.)

3. Configure IS-IS FRR:

   Enable IS-IS FRR to automatically calculate a backup next hop, or designate a backup next hop by using a referenced routing policy.

   • (Method 1.) Enable IS-IS FRR to automatically calculate a backup next hop:

     # Configure Switch A.

     <SwitchA> system-view
     [SwitchA] bfd echo-source-ip 2.2.2.2
     [SwitchA] isis 1
     [SwitchA-isis-1] fast-reroute auto
     [SwitchA-isis-1] quit
     

     # Configure Switch B.

     <SwitchB> system-view
     [SwitchB] bfd echo-source-ip 3.3.3.3
     [SwitchB] isis 1
     [SwitchB-isis-1] fast-reroute auto
     [SwitchB-isis-1] quit
     

   • (Method 2.) Enable IS-IS FRR to designate a backup next hop by using a referenced routing policy:

     # Configure Switch A.

     <SwitchA> system-view
     [SwitchA] bfd echo-source-ip 2.2.2.2
     [SwitchA] ip prefix-list abc index 10 permit 4.4.4.4 32
     [SwitchA] route-policy frr permit node 10
     [SwitchA-route-policy-frr-10] if-match ip address prefix-list abc
     [SwitchA-route-policy-frr-10] apply fast-reroute backup-interface vlan-interface 100 backup-nexthop 12.12.12.2
     [SwitchA-route-policy-frr-10] quit
     [SwitchA] isis 1
     [SwitchA-isis-1] fast-reroute route-policy frr
     [SwitchA-isis-1] quit
     

     # Configure Switch B.

     <SwitchB> system-view
     [SwitchB] bfd echo-source-ip 3.3.3.3
     [SwitchB] ip prefix-list abc index 10 permit 1.1.1.1 32
     [SwitchB] route-policy frr permit node 10
     [SwitchB-route-policy-frr-10] if-match ip address prefix-list abc
     [SwitchB-route-policy-frr-10] apply fast-reroute backup-interface vlan-interface 101 backup-nexthop 24.24.24.2
     [SwitchB-route-policy-frr-10] quit
     [SwitchB] isis 1
     [SwitchB-isis-1] fast-reroute route-policy frr
     [SwitchB-isis-1] quit
     

# Display route 4.4.4.4/32 on Switch A to view the backup next hop information.

[SwitchA] display ip routing-table 4.4.4.4 verbose

Summary Count : 1

Destination: 4.4.4.4/32
   Protocol: ISIS            Process ID: 1
  SubProtID: 0x1                    Age: 04h20m37s
       Cost: 10              Preference: 10
        Tag: 0                    State: Active Adv
  OrigTblID: 0x0                OrigVrf: default-vrf
    TableID: 0x2                 OrigAs: 0
      NibID: 0x26000002          LastAs: 0
     AttrID: 0xffffffff        Neighbor: 0.0.0.0
      Flags: 0x1008c        OrigNextHop: 13.13.13.2
      Label: NULL           RealNextHop: 13.13.13.2
    BkLabel: NULL             BkNextHop: 12.12.12.2
  Tunnel ID: Invalid          Interface: Vlan-interface200
BkTunnel ID: Invalid        BkInterface: Vlan-interface100

# Display route 1.1.1.1/32 on Switch B to view the backup next hop information.

[SwitchB] display ip routing-table 1.1.1.1 verbose

Summary Count : 1

Destination: 1.1.1.1/32
   Protocol: ISIS            Process ID: 1
  SubProtID: 0x1                    Age: 04h20m37s
       Cost: 10              Preference: 10
        Tag: 0                    State: Active Adv
  OrigTblID: 0x0                OrigVrf: default-vrf
    TableID: 0x2                 OrigAs: 0
      NibID: 0x26000002          LastAs: 0
     AttrID: 0xffffffff        Neighbor: 0.0.0.0
      Flags: 0x1008c        OrigNextHop: 13.13.13.1
      Label: NULL           RealNextHop: 13.13.13.1
    BkLabel: NULL             BkNextHop: 24.24.24.2
  Tunnel ID: Invalid          Interface: Vlan-interface200
BkTunnel ID: Invalid        BkInterface: Vlan-interface101