This topic explains interoperability and backward compatibility considerations for Spanning Tree Protocols (PVST+, MSTP, and Rapid PVST+) in mixed network environments.
In a mixed MSTP and PVST+ network, the Common Spanning Tree (CST) root must be inside the MST backbone, and a PVST+ switch cannot connect to multiple MST regions.
When a network contains switches running Rapid PVST+ and switches running PVST+, configure the Rapid PVST+ switches and PVST+ switches for different Spanning Tree instances. In Rapid PVST+ spanning-tree instances, use a Rapid PVST+ switch as the root. In PVST+ instances, use a PVST+ switch as the root. The PVST+ switches should be at the edge of the network.
All stack members run the same version of Spanning Tree (all PVST+, all Rapid PVST+, or all MSTP).
PVST+, MSTP, and Rapid-PVST+ Interoperability and Compatibility:
| PVST+ | MSTP | Rapid PVST+ | Interoperability and Compatibility |
|---|---|---|---|
| PVST+ | Yes | Yes (with restrictions) | Yes (reverts to PVST+) |
| MSTP | Yes (with restrictions) | Yes | Yes (reverts to PVST+) |
| Rapid PVST+ | Yes (reverts to PVST+) | Yes (reverts to PVST+) | Yes |