# Multiple Spanning Tree Protocol

With the Multiple Spanning Tree Protocol (MSTP or IEEE 802.1s), you can configure multiple instances of RSTP on the same switch. Each MSTP instance can include one or more VLANs. The operation of the MSTP is similar to the current Avaya proprietary STG.

In the MSTP mode, the 5000 Series switches support a maximum of one Common and Internal Spanning Tree (CIST) and seven Multiple Spanning Tree Instances (MSTI).

Within the CIST, the Internal Spanning Tree component is used only by devices from the same region (for which a regional root is elected). The Common (External) Spanning Tree component of the CIST is used by devices from different regions or between devices with different STP modes.

| Note
| you can access the MSTP menu command only when the switch is operating in the MSTP mode.