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| 3.8 |  | RSTP and MST Configuration |
| 3.8.2 |  | RSTP and MSTP configuration guidelines |

The configuration guidelines for RSTP and MSTP are:

- Per-VLAN RSTP is not supported (PVRST). When MST is enabled using the spanning-tree mode mst global configuration command, RSTP is enabled.
- PVST, PVST+ and MSTP are supported, but only one version can be active at any time; all VLANs run PVST, or all VLANs run MSTP.
- VTP propagation of the MST configuration is not supported. Manually configure the MST configuration (region name, revision number, and VLAN-to-instance mapping) on each switch within the MST region by using the command-line interface (CLI) or through the SNMP support.
- For load balancing across redundant paths in the network to work, all VLAN-to-instance mapping assignments must match. Otherwise, all traffic flows on a single link.
- All MST boundary ports must be forwarding for load balancing between a PVST+ and an MST cloud. For this to happen, the IST master of the MST cloud should also be the root of the CST. If the MST cloud consists of multiple MST regions, one of the MST regions must contain the CST root, and all of the other MST regions must have a better path to the root contained with the MST cloud than a path through the PVST+ cloud. It may be necessary to manually configure the switches in the clouds.
- Partitioning the network into a large number of regions is not recommended. However, if this situation is unavoidable, it is recommended that the switched LAN be partitioned into smaller LANs interconnected by routers or non-Layer 2 devices.