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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
—
Release 8.1
78-15486-01
Chapter 7 Configuring Spanning Tree
Using MISTP-PVST+ or MISTP
Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
Bridge ID MAC ADDR 00-d0-02-27-9c-00
Bridge ID Priority 32769 (bridge priority:32768, sys ID ext:1)
VLANs mapped: 1,74
Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
Port Inst Port-State Cost Prio Portfast Channel_id
------------------------ ---- ------------- --------- ---- -------- ----------
1/1 1 forwarding 20000 32 disabled 0
3/1 1 forwarding 200000 32 disabled 0
3/25 1 forwarding 200000 32 disabled 0
3/26 1 forwarding 200000 32 disabled 0
3/27 1 forwarding 200000 32 disabled 0
3/28 1 forwarding 200000 32 disabled 0
3/29 1 forwarding 200000 32 disabled 0
3/30 1 forwarding 200000 32 disabled 0
7/1-4 1 blocking 5000 32 disabled 833
7/5 1 forwarding 20000 32 disabled 0
7/6 1 forwarding 20000 32 disabled 0
8/37 1 blocking 200000 32 disabled 0
8/38 1 blocking 200000 32 disabled 0
15/1 1 forwarding 20000 32 enabled 0
16/1 1 forwarding 20000 32 enabled 0
Console> (enable)
Configuring the MISTP Port Cost
You can configure the port cost of switch ports. When forwarding frames, the switch is more likely to
use ports with lower port costs. 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. Path cost is typically equal to 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 MISTP instance and verify the configuration:
Console> (enable) set spantree portcost 1/1 20000
Spantree port 1/1 path cost set to 20000.
Console> (enable) show spantree mistp-instance 1 active
Instance 1
Spanning tree mode MISTP
Spanning tree type ieee
Spanning tree instance enabled
Designated Root 00-05-31-40-64-00
Designated Root Priority 32769 (root priority:32768, sys ID ext:1)
Designated Root Cost 20000
Designated Root Port 1/1
VLANs mapped: 1,74
Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
Bridge ID MAC ADDR 00-d0-02-27-9c-00
Task
Command
Step 1
Configure the port cost for a switch port.
set spantree portcost mod_num/port_num cost
Step 2
Verify the port cost setting.
show spantree mistp-instance instance
[mod_num/port_num] active