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Configuration Guide - Reliability

CloudEngine 12800 and 12800E V200R002C50

This document describes the configurations of Reliability, including BFD Configuration, VRRP Configuration, DLDP Configuration, Smart Link and Monitor Link Configuration, EFM Configuration, and CFM Configuration.
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If a designated router (DR) on the shared network segment becomes faulty, Protocol Independent Multicast (PIM) neighbor relationships time out. This triggers a new DR election among PIM neighbors, interrupting multicast data transmission. The interruption period is at least as long as the timeout interval of the neighbor relationship and usually lasts several seconds.

After detecting a fault on the peer, BFD immediately instructs the PIM module to trigger a new DR election without waiting for the neighbor relationship to time out.

BFD for PIM can quickly detect faults on the Assert winner and is also applicable to Assert election on a shared network segment.

Table 2-4 lists PIM convergence time.

Table 2-4 PIM convergence time

BFD Session

Link Fault Detection Mechanism

Convergence Time

Not bound

Neighbor relationship timeout

Measured in seconds


BFD session in Down state

Measured in milliseconds


Figure 2-10 BFD for PIM

In Figure 2-10, on the shared network segment connected to user hosts, the downstream interface on SwitchC, Interface1, and the downstream interface on SwitchD, Interface2, establish a PIM BFD session and send BFD control packets to monitor the link status.

SwitchC functions as the DR and Interface1 is responsible for forwarding multicast data. If Interface1 becomes faulty, BFD quickly notifies the RM of the session status and the RM notifies the PIM module. The PIM module then triggers a new DR election. SwitchD quickly begins functioning as the new DR and Interface2 begins forwarding multicast data to the receivers.

Updated: 2019-03-21

Document ID: EDOC1000166606

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