Allied Telesis AT-GS950/8 - Manual (Page 333)

AT-GS950/8 Web Interface User Guide
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General Guidelines
Here are the guidelines for MSTIs:
 The AT-GS950/8 switch can support up to 31 spanning tree instances,
including the CIST.
 A MSTI can contain any number of VLANs.
 A VLAN can belong to only one MSTI at a time.
 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.