Implementing the Multiple Spanning Tree Protocol – MSTP
The Extended System ID

As with PVST, the 12-bit Extended System ID field is used in MST. In MST this field carries the MST instance number.

The MAC address is a single address representing a single switch. When the VLAN ID Extended System ID carrying the VLAN ID is appended to the switch MAC address, each VLAN on the switch is represented by a unique Bridge Identifier


Web Links