Technical Documentation

Configuring Nonstop Active Routing

This section includes the following topics:

Enabling Nonstop Active Routing

Nonstop active routing (NSR) 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:

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.

Note: When you enable nonstop active routing, you cannot enable automatic route distinguishers for multicast VPN routing instances. Automatic route distinguishers are enabled by configuring the route-distinguisher-id statement at the [edit routing-instances instance-name] hierarchy level; for more information, see the JUNOS VPNs Configuration Guide.

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.

Synchronizing the Routing Engine Configuration

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 fails.

If you configure the commit synchronize statement at the [edit system] hierarchy level and issue a commit in the master Routing Engine, the master configuration is automatically synchronized with the backup.

However, if the backup Routing Engine is down when you issue the commit, the JUNOS Software displays a warning and commits the candidate configuration in the master Routing Engine. When the backup Routing Engine comes up, its configuration will automatically be synchronized with the master.

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.

Verifying Nonstop Active Routing Operation

To see whether or not nonstop active routing is enabled, issue the show task replication command. For BGP nonstop active routing, you can also issue the show bgp replication command.

For more information about these commands, see the JUNOS System Basics and Services Command Reference and JUNOS Routing Protocols and Policies Command Reference, respectively.

When you enable nonstop active routing and issue routing-related operational mode commands on the backup Routing Engine (such as show route, show bgp neighbor, show ospf database, and so on), the output might not match the output of the same commands issued on the master Routing Engine.

To display BFD state replication status, issue the show bfd session command. The replicated flag appears in the output for this command when a BFD session has been replicated to the backup Routing Engine. For more information, see the JUNOS Routing Protocols and Policies Command Reference.


Published: 2010-04-28