Configure BFD for RIP (single hop echo detection for a specific destination)

As shown in Figure 12, VLAN-interface 100 of Switch A and Switch B runs RIP process 1. VLAN-interface 200 of Switch B and Switch C runs RIP process 1.

Configure a static route destined for 100.1.1.0/24 and enable static route redistribution into RIP on both Switch A and Switch C so Switch B can learn two routes destined for 100.1.1.0/24 through VLAN-interface 100 and VLAN-interface 200. The route redistributed from Switch A has a smaller cost than that redistributed from Switch C, so Switch B uses the route through VLAN-interface 200.

Enable BFD for RIP on VLAN-interface 100 of Switch A, and specify VLAN-interface 100 of Switch B as the destination. When a unidirectional link occurs (packets from Switch A can reach Switch B, but packets from Switch B cannot reach Switch A), BFD can quickly detect the link failure and notify RIP. Switch B then deletes the neighbor relationship and the route information learned on VLAN-interface 100, and does not receive or send any packets from VLAN-interface 100. When the route learned from Switch A ages out, Switch B uses the route destined for 100.1.1.1 24 through VLAN-interface 200.

1. Configure IP addresses for interfaces. (Details not shown.)

2. Configure basic RIP and enable BFD on the interfaces:

   # Configure Switch A.

   <SwitchA> system-view
   [SwitchA] rip 1
   [SwitchA-rip-1] network 192.168.2.0
   [SwitchA-rip-1] import-route static
   [SwitchA-rip-1] quit
   [SwitchA] interface vlan-interface 100
   [SwitchA-Vlan-interface100] rip bfd enable destination 192.168.2.2
   [SwitchA-Vlan-interface100] quit
   

   # Configure Switch B.

   <SwitchB> system-view
   [SwitchB] rip 1
   [SwitchB-rip-1] network 192.168.2.0
   [SwitchB-rip-1] network 192.168.3.0
   [SwitchB-rip-1] quit
   

   # Configure Switch C.

   <SwitchC> system-view
   [SwitchC] rip 1
   [SwitchC-rip-1] network 192.168.3.0
   [SwitchC-rip-1] import-route static cost 3
   [SwitchC-rip-1] quit
   

3. Configure BFD parameters on VLAN-interface 100 of Switch A.

   [SwitchA] bfd echo-source-ip 11.11.11.11
   [SwitchA] interface vlan-interface 100
   [SwitchA-Vlan-interface100] bfd min-echo-receive-interval 500
   [SwitchA-Vlan-interface100] return
   

4. Configure static routes:

   # Configure a static route on Switch A.

   [SwitchA] ip route-static 100.1.1.0 24 null 0
   

   # Configure a static route on Switch C.

   [SwitchA] ip route-static 100.1.1.0 24 null 0
   

   # Display BFD session information on Switch A.

   <SwitchA> 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
    3              192.168.2.1     192.168.2.2     Up       2000ms      vlan100
   

   # Display routes destined for 100.1.1.0/24 on Switch B.

   <SwitchB> display ip routing-table 100.1.1.0 24 verbose
   
   Summary Count : 1
   
   Destination: 100.1.1.0/24
      Protocol: RIP             Process ID: 1
     SubProtID: 0x1                    Age: 00h02m47s
          Cost: 1               Preference: 100
           Tag: 0                    State: Active Adv
     OrigTblID: 0x0                OrigVrf: default-vrf
       TableID: 0x2                 OrigAs: 0
         NBRID: 0x12000002          LastAs: 0
        AttrID: 0xffffffff        Neighbor: 192.168.2.1
         Flags: 0x1008c        OrigNextHop: 192.168.2.1
         Label: NULL           RealNextHop: 192.168.2.1
       BkLabel: NULL             BkNextHop: N/A
     Tunnel ID: Invalid          Interface: vlan-interface 100
   BkTunnel ID: Invalid        BkInterface: N/A
   

   # Display routes destined for 100.1.1.0/24 on Switch B when the link between Switch A and Switch B fails.

   <SwitchB> display ip routing-table 100.1.1.0 24 verbose
   
   Summary Count : 1
   
   Destination: 100.1.1.0/24
      Protocol: RIP             Process ID: 1
     SubProtID: 0x1                    Age: 00h21m23s
          Cost: 4               Preference: 100
           Tag: 0                    State: Active Adv
     OrigTblID: 0x0                OrigVrf: default-vrf
       TableID: 0x2                 OrigAs: 0
         NBRID: 0x12000002          LastAs: 0
        AttrID: 0xffffffff        Neighbor: 192.168.3.2
         Flags: 0x1008c        OrigNextHop: 192.168.3.2
         Label: NULL           RealNextHop: 192.168.3.2
       BkLabel: NULL             BkNextHop: N/A
     Tunnel ID: Invalid          Interface: vlan-interface 200
   BkTunnel ID: Invalid        BkInterface: N/A