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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
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Chapter 7 Configuring Spanning Tree
Configuring MST
Console> (enable) show spantree mst 3
Spanning tree mode MST
Instance 3
VLANs Mapped: 31-40
Designated Root 00-10-7b-bb-2f-00
Designated Root Priority 8195 (root priority:8192, sys ID ext:3)
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 8195 (bridge priority:8192, sys ID ext:3)
Port State Role Cost Prio Type
------------------------ ------------- ---- -------- ----
--------------------
6/1 forwarding BDRY 20000 32 P2P,
Boundary(PVST)
6/2 blocking BDRY 20000 32 P2P,
Boundary(PVST)
Configuring the MST Port Cost
You can configure the port cost of switch ports.The switch uses ports with lower port costs to forward
frames. Assign lower numbers to ports that are attached to faster media (such as full duplex) and higher
numbers to ports that are attached to slower media. The possible range is from 1–65,535. The default
differs for different media. The path cost is typically 1000 ÷ LAN speed in megabits per second.
To configure the port cost for a port, perform this task in privileged mode:
This example shows how to configure the port cost on an MST instance and verify the configuration:
Console> (enable) set spantree portcost 6/1 10000 mst
Spantree port 6/1 path cost set to 10000.
Console> (enable)
Console> (enable) show spantree mst 6/1
Edge Port: No, (Configured) Default
Link Type: P2P, (Configured) Auto
Port Guard: Default
Boundary: Yes (PVST)
Inst State Role Cost Prio VLANs
---- ------------- ---- --------- ----
-----------------------------------
0 forwarding ROOT 10000 32 1
1 forwarding BDRY 10000 32 2-20
2 forwarding BDRY 10000 32 21-30
3 forwarding BDRY 10000 32 31-40
4 forwarding BDRY 10000 32 41-50
Console> (enable)
Task
Command
Step 1
Configure the MST port cost for a switch port.
set spantree portcost mod/port cost [mst]
Step 2
Verify the port cost setting.
show spantree mst [instance | mod/port]