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Configuring Nonstop Bridging on EX Series Switches (CLI Procedure)


This task uses Junos OS for EX Series switches that do not support the Enhanced Layer 2 Software (ELS) configuration style. If your switch runs software that supports ELS, see Configuring Nonstop Bridging on Switches (CLI Procedure).

You can configure nonstop bridging (NSB) to provide resilience for Layer 2 protocol sessions on an EX Series switch with redundant Routing Engines.

Nonstop bridging operates by synchronizing all protocol information for NSB-supported Layer 2 protocols between the primary and backup Routing Engines. If the switch has a Routing Engine switchover, the NSB-supported Layer 2 protocol sessions remain active because they are already synchronized on the backup Routing Engine. The Routing Engine switchover is transparent to neighbor devices, which do not detect any changes related to the Layer 2 protocol sessions on the switch.

To configure nonstop bridging:

  1. Enable graceful Routing Engine switchover (GRES):
  2. Configure the switch to always synchronize configuration changes between the Routing Engines:

    If you try to commit a configuration in which nonstop bridging is configured but synchronization of configuration changes is not configured, the configuration is not committed.

  3. Enable nonstop bridging:

    There is no requirement to start both Routing Engines simultaneously. If the backup Routing Engine is not up when you commit the configuration, the candidate configuration is committed in the primary Routing Engine. When the backup Routing Engine comes online, the configuration is automatically synchronized.