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Option: Configuring VPLS Nonstop Active Routing

Nonstop active routing (NSR) enables a routing platform with redundant Routing Engines to switch from a primary Routing Engine to a backup Routing Engine without alerting peer nodes that a change has occurred. Nonstop active routing uses the same infrastructure as graceful Routing Engine switchover to preserve interface and kernel information. However, nonstop active routing also preserves routing information and protocol sessions by running the routing protocol process (rpd) on both Routing Engines. The logical interface, next-hop router, and both advertised and received labels are preserved. In addition, nonstop active routing preserves TCP connections maintained in the kernel.

Nonstop active routing requires you to configure graceful Routing Engine switchover (GRES). To enable graceful Routing Engine switchover, include the graceful-switchover statement at the [edit chassis redundancy] hierarchy level:



[edit chassis redundancy]
graceful-switchover;

By default, nonstop active routing is disabled. To enable nonstop active routing, include the nonstop-routing statement at the [edit routing-options] hierarchy level:



[edit routing-options]
nonstop-routing;

To disable nonstop active routing, remove the nonstop-routing statement from the [edit routing-options] hierarchy level.

To enable the routing platform to switch over to the backup Routing Engine when the routing protocol process (rpd) fails rapidly three times in succession, include the other-routing-engine statement at the [edit system processes routing failover] hierarchy level.

For more information about the other-routing-engine statement, see the JUNOS System Basics Configuration Guide.

When you configure nonstop active routing, you must also include the commit synchronize statement at the [edit system] hierarchy level so that configuration changes are synchronized on both Routing Engines:



[edit system]
commit synchronize;

If you try to commit the nonstop active routing configuration without including the commit synchronize statement, the commit operation fails.

If you issue the commit synchronize command at the [edit] hierarchy level on the backup Routing Engine, the JUNOS system software displays a warning and commits the candidate configuration.

Note: A newly inserted backup Routing Engine automatically synchronizes its configuration with the master Routing Engine configuration.

When you configure nonstop active routing, you can bring the backup Routing Engine online after the master Routing Engine is already running. There is no requirement to start the two Routing Engines simultaneously.

To see whether or not nonstop active routing is enabled, issue the show task replication command.

Note: You must issue the show task replication command on the master Routing Engine. This command is not supported on the backup Routing Engine.

For more information on this command, see the JUNOS System Basics and Services Command Reference.

To trace the label and logical interface association that VPLS receives from the kernel replication state, include the nsr-synchronization statement at the [edit routing-options traceoptions flag] hierarchy level. This flag also traces the Layer 2 VPN signaling state replicated from routes advertised by BGP.



[edit routing-options]
traceoptions {
flag nsr-synchronization;
}

The following example enables graceful Routing Engine switchover, nonstop active routing, and nonstop active routing trace options for VPLS.



[edit]
system commit {
synchronize;
}
chassis {


redundancy {

graceful-switchover; # This
enables graceful Routing Engine switchover on the # routing platform.
}


}
routing-options {

nonstop-routing; # This enables
nonstop active routing on the routing platform.


traceoptions {
flag nsr-synchronization;
}


}

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