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CLI-based Configuration Guide - Reliability

AR100, AR120, AR150, AR160, AR200, AR1200, AR2200, AR3200, and AR3600 V200R010

This document provides guidance for configuring reliability services, including interface backup, BFD, VRRP, and EFM.
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Association Between VRRP and BFD to Implement a Rapid Active/Standby Switchover

Association Between VRRP and BFD to Implement a Rapid Active/Standby Switchover

A VRRP group sends and receives VRRP Advertisement packets to determine the master and backup statuses. When a VRRP group is faulty, the backup with the highest priority detects the fault and switches to the master after the Master_Down_Interval timer expires. The switchover period is at least 3s. During the switchover period, service traffic is still sent to the original master, causing user traffic loss. Association between VRRP and BFD prevents traffic loss. After a BFD session is configured between the master and the backup, and the BFD session is bound to the VRRP group, the BFD session detects connectivity of the VRRP group. After detecting a fault, the BFD session notifies the VRRP group of an active/standby switchover. This mechanism implements millisecond-level switchover and reduces traffic loss.

Table 7-3  VRRP and BFD association modes

Association Mode

Usage Scenario

VRRP Status Change

BFD Support

Association between a VRRP group and a common BFD session

A backup monitors the status of the master in a VRRP group. A common BFD session monitors the link between the master and backup.

If the BFD session detects a fault and goes Down, the BFD module notifies the VRRP group of the status change. After receiving the notification, the VRRP group changes VRRP priorities of devices and determines whether to perform an active/standby switchover.

The VRRP-enabled device must be enabled with BFD.

The VRRP group can be bound to a static BFD session or a static BFD session with automatically negotiated discriminators.

Figure 7-8  Association between a VRRP group and a common BFD session

As shown in Figure 7-8, a VRRP group is configured between RouterA and RouterB. RouterA is the master and RouterB is the backup. User traffic is forwarded through RouterA. Delayed preemption is configured on RouterA and immediate preemption is configured on RouterB. BFD sessions are configured on RouterA and RouterB and association between VRRP and BFD is configured on RouterB.

When a fault occurs in the VRRP group, BFD rapidly detects the fault and instructs RouterB to increase the priority. In this case, RouterB has a higher priority than RouterA. RouterB becomes the master and forwards user traffic. This implements a rapid active/standby switchover.

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Updated: 2019-08-12

Document ID: EDOC1100034076

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