Configuring BFD for RIP (bidirectional control detection mode)

Network requirements

In the following figure, Switch A is connected to Switch C through Switch B. VLAN-interface 100 on Switch A, VLAN-interface 200 on Switch C, and VLAN-interface 200 and VLAN-interface 100 on Switch B run RIP process 1.

Configure a static route to Switch C on Switch A, and configure a static route to Switch A on Switch C. Enable BFD on VLAN-interface 100 of Switch A and VLAN-interface 200 of Switch C.

Switch A is connected to Switch C through Switch D. VLAN-interface 300 on Switch A runs RIP process 2; VLAN-interface 400 on Switch C, and VLAN-interface 300 and VLAN-interface 400 on Switch D run RIP process 1.

Enable static route redistribution into RIP on Switch A and Switch C so that Switch A and Switch C have routes to send to each other. Switch A learns the static route sent by Switch C, the output interface is the interface connected to Switch B.

Configure BFD so that when the link between Switch B and Switch C fails, BFD can quickly detect the link failure and notify it to RIP, and the BFD session goes down. In response, RIP deletes the neighbor relationship with Switch C and the route information received from Switch C. Then, Switch A learns the static route sent by Switch C, the output interface of the route is the interface connected to Switch D.

Figure 16: Network diagram

Configuration procedure

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

Configure RIP basic functions and enable static route redistribution into RIP so that Switch A and Switch C have routes to send to each other:

# Configure Switch A.

<SwitchA> system-view
[SwitchA] rip 1
[SwitchA-rip-1] version 2
[SwitchA-rip-1] undo summary
[SwitchA-rip-1] network 192.168.1.0
[SwitchA-rip-1] peer 192.168.2.2
[SwitchA-rip-1] undo validate-source-address
[SwitchA-rip-1] import-route static
[SwitchA-rip-1] quit
[SwitchA] interface vlan-interface 100
[SwitchA-Vlan-interface100] rip bfd enable
[SwitchA-Vlan-interface100] quit
[SwitchA] rip 2
[SwitchA-rip-2] version 2
[SwitchA-rip-2] undo summary
[SwitchA-rip-2] network 192.168.3.0
[SwitchA-rip-2] quit

# Configure Switch C.

<SwitchC> system-view
[SwitchC] rip 1
[SwitchC-rip-1] version 2
[SwitchC-rip-1] undo summary
[SwitchC-rip-1] network 192.168.2.0
[SwitchC-rip-1] network 192.168.4.0
[SwitchC-rip-1] peer 192.168.1.1
[SwitchC-rip-1] undo validate-source-address
[SwitchC-rip-1] import-route static
[SwitchC-rip-1] quit
[SwitchC] interface vlan-interface 200
[SwitchC-Vlan-interface200] rip bfd enable
[SwitchC-Vlan-interface200] quit

# Configure Switch D.

<SwitchD> system-view
[SwitchD] rip 1
[SwitchD-rip-1] version 2
[SwitchD-rip-1] undo summary
[SwitchD-rip-1] network 192.168.3.0
[SwitchD-rip-1] network 192.168.4.0

Configure BFD parameters:

# Configure Switch A.

[SwitchA] bfd session init-mode active
[SwitchA] interface vlan-interface 100
[SwitchA-Vlan-interface100] bfd min-transmit-interval 500
[SwitchA-Vlan-interface100] bfd min-receive-interval 500
[SwitchA-Vlan-interface100] bfd detect-multiplier 7
[SwitchA-Vlan-interface100] quit

# Configure Switch C.

[SwitchC] bfd session init-mode active
[SwitchC] interface vlan-interface 200
[SwitchC-Vlan-interface200] bfd min-transmit-interval 500
[SwitchC-Vlan-interface200] bfd min-receive-interval 500
[SwitchC-Vlan-interface200] bfd detect-multiplier 7
[SwitchC-Vlan-interface200] quit

Configure static routes.
# Configure a static route to Switch C on Switch A.
```
[SwitchA] ip route-static 192.168.2.0 24 vlan-interface 100 192.168.1.2
[SwitchA] ip route-static 101.1.1.0 24 null 0
[SwitchA] quit
```
# Configure a static route to Switch A on Switch C.
```
[SwitchC] ip route-static 192.168.1.0 24 vlan-interface 200 192.168.2.1
[SwitchC] ip route-static 100.1.1.0 24 null 0
```
IMPORTANT:
If you specify null 0 interface as the output interface for a static route, do not specify the IP address of a directly connected network as the destination IP address.

Verify the configuration:

# Display the BFD session information on Switch A.

<SwitchA> display bfd session
Total Session Num: 1            Init Mode: Active
 Session Working Under Ctrl Mode:
 LD/RD         SourceAddr      DestAddr        State Holdtime Interface
 6/3           192.168.1.1     192.168.2.2     Up    1700ms   vlan100

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

<SwitchA> display ip routing-table 100.1.1.0 24 verbose
Routing Table : Public
Summary Count : 2
  Destination: 100.1.1.0/24
     Protocol: RIP             Process ID: 1
   Preference: 100                   Cost: 1
 IpPrecedence:                    QosLcId:
      NextHop: 192.168.2.2      Interface: vlan-interface 100
    BkNextHop: 0.0.0.0         BkInterface:
  RelyNextHop: 192.168.1.2        Neighbor: 192.168.2.2
    Tunnel ID: 0x0                  Label: NULL
  BKTunnel ID: 0x0                BKLabel: NULL
        State: Active GotQ            Age: 00h00m47s
          Tag: 0
  Destination: 100.1.1.0/24
     Protocol: RIP             Process ID: 2
   Preference: 100                   Cost: 2
 IpPrecedence:                    QosLcId:
      NextHop: 192.168.3.2      Interface: vlan-interface 300
    BkNextHop: 0.0.0.0        BkInterface:
  RelyNextHop: 0.0.0.0          Neighbor : 192.168.3.2
    Tunnel ID: 0x0                  Label: NULL
  BKTunnel ID: 0x0                BKLabel: NULL
        State: Inactive Adv           Age: 00h12m50s
        Tag: 0

When the link over VLAN-interface 100 fails, Switch A quickly detects the link state change.

# Display the BFD information on Switch A.

<SwitchA> display bfd session

Switch A has deleted the BFD session on VLAN-interface 100 to Switch C and displays no output.

# Display the RIP routes of RIP process 1 on Switch A.

<SwitchA> display rip 1 route
 Route Flags: R - RIP, T - TRIP
              P - Permanent, A - Aging, S - Suppressed, G - Garbage-collect
 ----------------------------------------------------------------------------

The output show that the RIP route learned from Switch C no longer exists.

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

<SwitchA> display ip routing-table 100.1.1.0 24 verbose
Routing Table : Public
Summary Count : 1

  Destination: 100.1.1.0/24
     Protocol: RIP             Process ID: 2
   Preference: 100                   Cost: 2
 IpPrecedence:                    QosLcId:
      NextHop: 192.168.3.2      Interface: vlan-interface 300
    BkNextHop: 0.0.0.0        BkInterface:
  RelyNextHop: 0.0.0.0          Neighbor : 192.168.3.2
    Tunnel ID: 0x0                  Label: NULL
  BKTunnel ID: 0x0                BKLabel: NULL
        State: Active Adv             Age: 00h18m40s
          Tag: 0

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