5-18
Multiple Instance Spanning-Tree Operation
802.1s Multiple Spanning Tree Protocol (MSTP)
– Hello Time (used if the switch operates as the root device.)
spanning-tree hello-time
– Maximum age to allow for STP packets before discarding
spanning-tree maximum-age
– 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-port for
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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