Establishing a BFD Session

Procedure

1. Run system-view

   The system view is displayed.

2. According to whether BFD detects an IPv4 or IPv6 link, perform either of the following operations:
   • According to whether the remote end is configured with an IP address, run either of the following commands to configure a BFD binding relationship:

     • To bind the BFD session to a Layer 3 interface with an IP address, run bfd session-name bind peer-ip peer-ip [ vpn-instance vpn-name ] [ interface interface-type interface-number ] [ source-ip source-ip ]

       A BFD session for IPv4 is bound to a Layer 3 interface.

       

       • If a single-hop BFD session for IPv4 is created for the first time, a peer IPv4 address must be specified for the BFD session, and the BFD session must be bound to the local interface. The binding cannot be modified after being created.
       • When a BFD session for IPv4 is created, the system checks only the validity of the IPv4 address format. Binding the BFD session for IPv4 to an incorrect remote or local IPv4 address results in a failure in establishing the BFD session for IPv4.
       • If BFD and unicast reverse path forwarding (URPF) are used together, source-ip must be configured correctly before a BFD session is bound to the IPv4 address to prevent BFD packets from being discarded. URPF checks the format of the source IPv4 addresses in received packets and discards the packets whose source IPv4 addresses are incorrect.

     • To bind the BFD session to a Layer 2 interface or a Layer 3 member interface without an IP address, run bfd session-name bind peer-ip default-ip interface interface-type interface-number [ source-ip source-ip ]

       A BFD session for IPv4 is bound to an interface.

       

       • To bind the BFD session to a sub-interface for dot1q VLAN tag termination:

         1. Run control-vid
         2. Run dot1q termination vid
         3. Run dot1q (BFD session view)

       • To bind the BFD session to a sub-interface for QinQ VLAN tag termination:

         1. Run control-vid
         2. Run qinq termination pe-vid ce-vid
         3. Run qinq (BFD session view)

   • Run bfd session-name bind peer-ipv6 peer-ipv6 [ vpn-instance vpn-name ] [ interface interface-type interface-number ] [ source-ipv6 source-ipv6 ]

     A BFD session for IPv6 is bound to an interface.

     

     • If a single-hop BFD session for IPv6 is created for the first time, the BFD session must be bound to the remote IPv6 address and the local interface. The binding cannot be modified after being created.
     • When a BFD session for IPv6 is created, the system checks only the validity of the IPv6 address format. Binding the BFD session for IPv6 to an incorrect remote or local IPv6 address results in a failure in establishing the BFD session for IPv6.
     • If BFD and URPF are used together, source-ip must be configured correctly before a BFD session is bound to the interface to prevent BFD packets from being discarded. URPF checks the format of the source IPv6 addresses in received packets and discards the packets whose source IPv6 addresses are incorrect.

3. Run discriminator local discr-value

   The local discriminator of the BFD session is created.

4. Run discriminator remote discr-value

   The remote discriminator of the BFD session is created.

   

   The local and remote discriminators on the two ends of a BFD session must be correctly associated. That is, the local discriminator of the local device must be the same as the remote discriminator of the remote device, and the remote discriminator of the local device must be the same as the local discriminator of the remote device. If the association is incorrect, a BFD session cannot be set up.

5. Run commit

   The configuration is committed.