VSX configuration synchronization

VSX configuration synchronization simplifies VSX solution management, reduces configuration misconfiguration and drift across VSX peer switches. With configuration synchronization enabled, the primary peer configuration is synced to the secondary peer. This synchronization is controlled in an opt-in manner by enabling VSX synchronization on a section of configuration.

If one or more of the following scenarios occur, the secondary switch will receive the configuration update after it fulfills synchronization requirements and is fully enabled:
  • The secondary switch is not currently present.

  • The secondary switch is not currently connected to the primary switch through the ISL.

  • The secondary switch is not currently configured for VSX configuration synchronization at the time VSX configuration synchronization is enabled on the primary switch.

You can only enable a specific configuration for syncing through the vsx-sync CLI extension on the primary switch. This extension is blocked on the secondary peer switch except when VSX configuration-synchronization is disabled or the ISL link is down.

Features supporting VSX

You can enable VSX synchronization at:

VSX synchronization requirements

  • Software image versions must be the same on both switches.

  • The output from the show vsx status command must show in-sync for Config Sync Status.

  • Primary and secondary roles configured.

  • An interswitch link must be configured.

  • When enabling VSX synchronization under a physical interface, a VLAN interface, or a VSX LAG, create on the secondary switch the physical interface, VLAN interface, or VSX LAG with the same name and routing setting as on the primary switch. For example, if the primary switch has a physical interface of 1/1/1, you must create another physical interface of 1/1/1 on the secondary switch. Also, if the primary VSX switch has routing enabled, the secondary switch must have routing enabled. Once the name and routing information is the same, VSX synchronization synchronizes the additional configuration information from the primary VSX switch to the secondary VSX switch.


It is recommended to:

  • Enable keepalive for preventing traffic loss during an ISL link failure.

  • Assign a common system MAC to prevent traffic loss in cases when the secondary VSX switch is restored before the primary VSX switch.