MSTP+ Overview
In the standard IEEE 802.1s MSTP all VLANs are automatically placed under CIST control so that the entire switch is controlled by the MSTP. The MSTP+ feature is an enhancement that allows you to exclude one or more VLANs from the MSTP scope and configure them in a non-MSTP topology. These VLANs are considered free VLANs and can run any Layer 2 protocols such as PVST/PVRST, MRP, VSRP, or any pure Layer 3 protocols.
You must ensure all the connected devices are properly configured, create the MSTP instances, and assign the VLANs to those instances. These instances must be configured on all devices that interoperate with the same VLAN assignments.
The following table lists the protocols that can run under free VLANs along with the MSTP+.
Protocols Compatible with MSTP+
| Protocols | Compatible with MSTP+ |
|---|---|
| Spanning tree single (802.1D) | No |
| Rapid spanning tree single (802.1w) | No |
| MCT | No |
| Per-VLAN spanning tree (STP, RSTP) | Yes |
| VSRP | Yes |
| MRP | Yes |
| All Layer 3 protocols (pure Layer 3 network) | Yes |
This means that you can create an independent Layer 3 topology even when on a switch that is configured with MSTP. The MSTP convergence does not affect the Layer 3 topology.
You can switch between non-MSTP, MSTP, and MSTP+ modes.