MSTP with VSX guidelines

  • Path cost is not allowed to be configured on the ISL port.

  • Layer 2 link connected parallel to ISL link is blocked by MSTP.

  • Do not configure port-specific spanning tree configurations on the ISL.

  • Multiple instances are supported though (default + 64).

  • Topology changes for VSX LAGs are accounted on the active multichassis LAG role only.

  • MSTP is supported in both VSX and non-VSX environments.

  • The common bridge ID continues to be used even after the VSX split brain scenario is identified.

  • STP configurations on VSX LAG ports must be the same on VSX switches. Use vsx-sync mclag-interfaces command for syncing STP and LAG interface configurations.

  • Run the show running-config spanning tree and show running-config spanning tree vsx-peer commands for verifying that the following global parameters are the same on VSX switches:
    • STP mode.

    • STP region configuration for MSTP (config-name and config-revision)

    • STP instance to VLAN mapping

    • STP instance priority

Alternatively, you can also use vsx-sync stp-global to sync all the above mentioned global commands.