IS-IS FRR configuration example

Switch S, Switch A, and Switch D belong to the same IS-IS routing domain as illustrated in Figure 68. Configure IS-IS FRR so that when the link between Switch S and Switch D 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 D, and Switch S can communicate with each other at Layer 3. (Details not shown.)

3. Configure IS-IS FRR:

   You can enable IS-IS FRR to either automatically calculate a backup next hop, or to designate a backup next hop by using a referenced routing policy.

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

   # Configure Switch S.

   <SwitchS> system-view
   [SwitchS] bfd echo-source-ip 1.1.1.1
   [SwitchS] isis 1
   [SwitchS-isis-1] fast-reroute auto
   [SwitchS-isis-1] quit
   

   # Configure Switch D.

   <SwitchD> system-view
   [SwitchD] bfd echo-source-ip 4.4.4.4
   [SwitchD] isis 1
   [SwitchD-isis-1] fast-reroute auto
   [SwitchD-isis-1] quit
   

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

   # Configure Switch S.

   <SwitchS> system-view
   [SwitchS] bfd echo-source-ip 1.1.1.1
   [SwitchS] ip ip-prefix abc index 10 permit 4.4.4.4 32
   [SwitchS] route-policy frr permit node 10
   [SwitchS-route-policy] if-match ip-prefix abc
   [SwitchS-route-policy] apply fast-reroute backup-interface vlan-interface 100 backup-nexthop 12.12.12.2
   [SwitchS-route-policy] quit
   [SwitchS] isis 1
   [SwitchS-isis-1] fast-reroute route-policy frr
   [SwitchS-isis-1] quit
   

   # Configure Switch D.

   <SwitchD> system-view
   [SwitchD] bfd echo-source-ip 4.4.4.4
   [SwitchD] ip ip-prefix abc index 10 permit 1.1.1.1 32
   [SwitchD] route-policy frr permit node 10
   [SwitchD-route-policy] if-match ip-prefix abc
   [SwitchD-route-policy] apply fast-reroute backup-interface vlan-interface 101 backup-nexthop 24.24.24.2
   [SwitchD-route-policy] quit
   [SwitchD] isis 1
   [SwitchD-isis-1] fast-reroute route-policy frr
   [SwitchD-isis-1] quit
   

4. Verify the configuration:

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

   [SwitchS] display ip routing-table 4.4.4.4 verbose
   Routing Table : Public
   Summary Count : 1
   
     Destination: 4.4.4.4/32
        Protocol: ISIS            Process ID: 1
      Preference: 10                    Cost: 10
    IpPrecedence:                    QosLcId:
         NextHop: 13.13.13.2       Interface: Vlan-interface200
       BkNextHop: 12.12.12.2     BkInterface: Vlan-interface100
     RelyNextHop: 0.0.0.0          Neighbor : 0.0.0.0
       Tunnel ID: 0x0                  Label: NULL
     BKTunnel ID: 0x0                BKLabel: NULL
           State: Active Adv             Age: 00h01m27s
             Tag: 0
   

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

   [SwitchD] display ip routing-table 1.1.1.1 verbose
   Routing Table : Public
   Summary Count : 1
   
     Destination: 1.1.1.1/32
        Protocol: ISIS            Process ID: 1
      Preference: 10                    Cost: 10
    IpPrecedence:                    QosLcId:
         NextHop: 13.13.13.1       Interface: Vlan-interface200
       BkNextHop: 24.24.24.2     BkInterface: Vlan-interface101
     RelyNextHop: 0.0.0.0          Neighbor : 0.0.0.0
       Tunnel ID: 0x0                  Label: NULL
     BKTunnel ID: 0x0                BKLabel: NULL
           State: Active Adv             Age: 00h01m27s
             Tag: 0