Allied Telesis AT-S63 - Manual (Page 238)

Chapter 22: Multiple Spanning Tree Protocol
238 Section V: Spanning Tree Protocols
MSTI Guidelines
Following are several guidelines to keep in mind about MSTIs:
ˆ The AT-9400 Switch can support up to 16 spanning tree instances,
including the CIST.
ˆ A MSTI can contain any number of VLANs.
ˆ A VLAN can belong to only one MSTI at a time.
ˆ A switch port can belong to more than one spanning tree instance at a
time by being an untagged and tagged member of VLANs belonging to
different MSTI’s. This is possible because a port can be in different
MSTP states for different MSTI’s simultaneously. For example, a port
can be in the MSTP blocking state for one MSTI and the forwarding
state for another spanning tree instance. For further information, refer
to “Ports in Multiple MSTIs,” next.
ˆ A router or Layer 3 network device is required to forward traffic
between different VLANs.