Multiple Instance Spanning-Tree Operation

802.1s Multiple Spanning Tree Protocol (MSTP)

Device spanning-tree priority. Specifies the priority value used along with the switch MAC address to determine which device is root. The lower a priority value, the higher the priority.

spanning-tree priority

2.Configure MST instances.

Configure one instance for each VLAN group that you want to operate as an active topology within the region to which the switch belongs. When you create the instance, you must include a minimum of one VID. You can add more VIDs later if desired.

spanning-tree instance < 1 - 16 > vlan < vid >

To move a VLAN from one instance to another, first use no spanning- tree instance < n > vlan < vid > to unmap the VLAN from the current instance, then add the VLAN to the other instance. (While the VLAN is unmapped from an MSTI, it is associated with the region’s IST instance.)

3.Configure the priority for each instance.

spanning-tree instance < n > priority < n >

4.Configure MST instance port parameters. Enable admin-edge-portfor ports connected to end nodes (page 23), but leave it disabled (the default) for connections to another switch, a bridge, or a hub. Set the path cost value for the port(s) used by a specific MST instance. Leaving this setting at the default auto allows the switch to calculate the path-cost from the link speed.

spanning-tree instance < 1 - 16 ist > port-list < port-list >

5.Enable spanning-tree operation on the switch.

spanning-tree

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