7-53
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
—
Release 8.1
78-15486-01
Chapter 7 Configuring Spanning Tree
Configuring MST
Console> (enable) show spantree mst 4
Spanning tree mode MST
Instance 4
VLANs Mapped: 41-50
Designated Root 00-10-7b-bb-2f-00
Designated Root Priority 32772 (root priority:32768, sys ID ext:4)
Designated Root Cost 0 Remaining Hops 20
Designated Root Port 1/0
Bridge ID MAC ADDR 00-10-7b-bb-2f-00
Bridge ID Priority 32772 (bridge priority:32768, sys ID ext:
4)
Port State Role Cost Prio Type
------------------------ ------------- ---- -------- -----------------
6/1 forwarding BDRY 5000 30 P2P,
Boundary(PVST)
6/2 blocking BDRY 20000 32 P2P,
Boundary(PVST)
Console> (enable)
Configuring the MST Port Instance Priority
You can set a port priority for an instance of MST. The port with the lowest priority for a specific MST
instance forwards frames for that instance. The port instance range is from 0–63. If all ports have the
same priority for an MST instance, the port with the lowest port number forwards frames for that
instance.
To configure the port instance priority on an MST instance, perform this task in privileged mode:
This example shows how to configure the port instance priority on an MST instance and verify the
configuration:
Console> (enable) set spantree portinstancepri 6/1 20 mst 2
Port 6/1 MST Instances 2 using portpri 20.
Port 6/1 MST Instances 0-1,3-15 using portpri 30.
Console> (enable)
Console> (enable)
Console> (enable) show spantree mst 2
Spanning tree mode MST
Instance 2
VLANs Mapped: 21-30
Designated Root 00-10-7b-bb-2f-00
Designated Root Priority 32770 (root priority:32768, sys ID ext:2)
Designated Root Cost 0 Remaining Hops 20
Designated Root Port 1/0
Task
Command
Step 1
Configure the port instance priority on an MST
instance.
set spantree portinstancepri mod/port
priority mst [instance]
Step 2
Verify the port instance priority setting.
show spantree mst [instance | mod/port]
