Improving The Convergence Time For Vrrp - Juniper EX9200 Features Manual

High Availability Feature Guide for EX9200 Switches
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Improving the Convergence Time for VRRP

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The VRRP unified ISSU takes care of VRRP only. Packet forwarding is the responsibility
of the Packet Forwarding Engine. The Packet Forwarding Engine unified ISSU should
ensure uninterrupted traffic flow.
VRRP is not affected by any change event during unified ISSU, for example, the
switchover of the master Routing Engine to backup or the backup Routing Engine to
master.
VRRP might stop and discard any running timer before entering into unified ISSU. This
means the expected action upon the expiry of the timer never takes place. However,
you can defer unified ISSU until the expiration of all running timers.
Unified ISSU at both local and remote routers cannot be done simultaneously.
Release
12.2
Understanding VRRP on page 119
Configuring Basic VRRP Support on page 130
You can enable faster convergence time for the configured Virtual Router Redundancy
Protocol (VRRP), thereby reducing the traffic restoration time to less than 1 second. To
improve the convergence time for the VRRP, perform the following tasks:
Configure the distributed periodic packet management process—When the VRRP
process is busy and does not send VRRP advertisements, the backup VRRP routers
might assume that the master router is down and take over as the master router,
causing unnecessary flaps. To address this problem and to reduce the load on the
VRRP process, Junos OS uses the distributed periodic packet management (PPM)
process to send VRRP advertisements on behalf of the VRRP process.
To configure the distributed PPM process, include the
at the [edit protocols vrrp]
Disable the skew timer—The skew timer in VRRP is used to ensure that two backup
routers do not switch to the master state at the same time in case of a failover situation.
When there is only one master router and one backup router in the network deployment,
you can disable the skew timer, thereby reducing the time required to transition to the
master state.
To disable the skew timer, include the
hierarchy level.
protocols vrrp]
Configure the number of fast advertisements that can be missed by a backup router
before it starts transitioning to the master state—The backup router waits until a
certain number of advertisement packets are lost after which it transitions to the master
state. This waiting time can be fatal in scenarios such as router failure or link failure.
Description
Junos OS Release 12.2 and later releases support VRRPv3.
hierarchy level.
skew-timer-disable
statement
delegate-processing
statement at the [edit
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