Configuring BFD for IPv4 PIM

Context

In a traditional multicast network, if the DR fails, the system elects a new DR only after the PIM neighbor relationship times out. The election takes several seconds, but a network interruption for several seconds will result in service losses for most enterprises.

To improve multicast networking sensitivity and reliability, BFD is introduced to PIM-SM to speed up system response upon a network interruption within milliseconds. BFD can detect the PIM neighbor status on a shared network segment. Once a network fault occurs, BFD reports the fault to the PIM module. The PIM module directly triggers the DR election without waiting for the timeout of the PIM neighbor relationship. The new DR replaces the faulty DR, reducing enterprise losses. BFD also applies to Assert election on the shared network segment, enabling the system to rapidly respond to Assert Winner interface faults.

Prerequisites

Before configuring BFD for IPv4 PIM, complete the following tasks:

• Configure unicast routing protocols.

• Configuring Basic PIM-SM Functions

Procedure

1. Access the system view.

   system-view

2. Enable BFD globally and enter the BFD view.

   bfd

3. Return to the system view.

   quit

4. Access the interface view.

   interface interface-type interface-number

5. Enable BFD for IPv4 PIM.

   pim bfd enable

   By default, BFD for IPv4 PIM is disabled.

6. Optional: Adjust PIM BFD parameter settings.

   pim bfd { min-tx-interval tx-value | min-rx-interval rx-value | detect-multiplier multiplier-value } ^*

   The negotiation mechanism of the actual sending interval, receiving interval, and detection interval of BFD packets is as follows:

   • Actual sending interval and receiving interval:

     • Actual sending interval = Max(Local min-tx-interval, Remote min-rx-interval)
     • Actual receiving interval = Max(Remote min-tx-interval, Local min-rx-interval)

   • Actual detection interval = Peer detect-multiplier x Max(Remote min-tx-interval, Local min-rx-interval)

   BFD parameters can be set on both sending and receiving ends, and both configurations take effect. If BFD parameters are also set for other parameters, the PIM BFD function may be affected. Check the configuration to prevent adverse impacts.

Verification

• display pim [ vpn-instance vpn-instance-name | all-instance ] bfd session statistics
• display pim [ vpn-instance vpn-instance-name | all-instance ] bfd session [ interface interface-type interface-number | neighbor neighbor-address ] ^*