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.

  • MSTP configuration synchronization between VSX peer switches is not supported. MSTP configurations have to be identical on VSX switches.

  • All port-specific spanning tree configurations are not recommended to configure on the ISL.

  • MSTP interregion and RPVST on VSX are not supported.

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

  • Use MSTP only on a VSX environment replacing loop protect.

  • To view the latest topology changes of the VSX peer, synchronize the time by using NTP (vsx-sync time command) and then enter the show spanning-tree mst <0-64> vsx-peer command.

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

  • Interoperability with other STP types is not supported with a direct connection to the VSX environment. The VSX pair is configured as a nonroot switch.

  • STP configurations on VSX LAG ports must be the same on VSX switches.

  • To verify that all switches are in the same MSTP region with the instance mapping to VLAN, run the following command: show spanning-tree mst-config

  • 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 MSTP

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

    • STP instance to VLAN mapping

    • STP instance priority