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Configuration Guide - IP Multicast

S7700 and S9700 V200R013C00

This document describes the configurations of IP multicast, including IP multicast basics, IGMP, MLD, IPv4 PIM, IPv6 PIM, MSDP, multicast VPN, layer 3 multicast CAC, IPv4 multicast route management, IPv6 multicast route management, IGMP snooping, MLD snooping, static multicast MAC address, multicast VLAN replication, layer 2 multicast CAC, multicast network management.
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Configuring PIM BFD

Configuring PIM BFD

Pre-configuration Tasks

Before configuring PIM BFD, complete the following tasks:

  • Configuring a unicast routing protocol to ensure normal unicast routing on the network
  • Enabling BFD globally using the bfd command
  • Enabling PIM-SM


On a PIM network, changes of link status between PIM neighbors will restart some PIM mechanisms, such as DR election or Assert winner election. For example, when the designated router (DR) on a shared network segment fails, PIM neighbors on the network segment trigger DR re-election only when the PIM neighbor relationships time out. Multicast data transmission is interrupted before a new DR is elected. The multicast service interruption time is longer than or equal to the neighbor relationship timeout interval, and is usually several seconds.

PIM Bidirectional Forwarding Detection (BFD) can detect link status changes on a shared network segment in milliseconds, enabling PIM devices to rapidly respond to failures of PIM neighbors. If a PIM BFD-capable interface does not receive any BFD packets from the DR within the detection interval, it considers that the DR has failed. Then BFD rapidly reports the session status to the route management (RM) module, which then reports the link status change to the PIM module. After receiving the notification, the PIM module triggers DR re-election immediately, without waiting for timeout of the neighbor relationship. This mechanism reduces the multicast service interruption time and improves reliability of multicast data transmission.

PIM BFD is applicable to the assert election on the shared network segment. In addition, it quickly responds to faults on the assert winner interface.

Default Settings

Table 4-19 lists the default settings of control parameters for PIM BFD messages.

Table 4-19  Default settings of control parameters for PIM BFD messages
Parameter Default Setting

Minimum sending interval

1000 ms

Minimum receiving interval

1000 ms

Local detection multiplier



  1. Run system-view

    The system view is displayed.

  2. Run interface interface-type interface-number

    The interface view is displayed.

  3. (Optional) On an Ethernet interface, run undo portswitch

    The interface is switched to Layer 3 mode.

    By default, an Ethernet interface works in Layer 2 mode.

  4. Run pim bfd enable

    PIM BFD is enabled.

  5. (Optional)Run pim bfd { min-tx-interval tx-value | min-rx-interval rx-value | detect-multiplier multiplier-value } *

    The parameters of PIM BFD are set.

    This operation is performed to set the minimum interval for sending the PIM BFD messages, the minimum interval for receiving the PIM BFD messages, and the local detection multiplier.

Verifying the Configuration

After PIM BFD is configured, you can run the following commands to check information about the PIM BFD session.

  • 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 ] *

Updated: 2019-04-08

Document ID: EDOC1100065742

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