MSTP configurations
VSX at the distribution layer with MSTP enabled
In the following figure, the VSX pair is configured as a root switch. All the ports of the VSX LAGs, non-VSX LAGs, and orphan ports are in a forwarding state. Bridge Protocol Data Units (BPDUs), generated by a VSX pair, are the same on all ports, including VSX LAG, non-VSX LAG, and orphan. All switches must be in the same MSTP region consisting of the same configuration name and revision number, as set by the
spanning-tree config-name
<CONFIG-NAME> and
spanning-tree config-revision
<REVISION-NUMBER> commands.
| Abbreviation | Definition |
|---|---|
| AB | Alternate blocking; the port is in a blocked state. |
| DF | Designated forwarding; the port is in a forwarding state. |
| RF | Root forwarding; the port is in a forwarding state. |
See Sample configurations for MSTP on VSX for the configuration for the topologies displayed in the figures in this topic.
In the following figure, the VSX pair is not a root switch for STP topology. One of the VSX LAG ports is in the blocking state for resolving an L2 network loop. The VSX LAG port is in a blocking state on both VSX peer switches.
Distribution VSX pair connected to the core switch (SVI solution)
In the following figure, the VSX switch could be either a root switch or a nonroot switch for STP topology. One of the uplinks connected from the distribution layer to the core switch is in a blocking state because the MSTP is enabled in a VSX pair connected to a core switch, but the SVP configured without MSTP is enabled.
This configuration might also cause the flooding of the MSTP BPDUs (VLAN unaware) based on the VLAN configuration. VLANs must be configured differently on both ports to avoid flooding back to another VSX pair. Configure the BPDU filter on L2 ports connected to the core switch so that these ports will be in a forwarding state.
