7-38
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 7 Configuring Spanning Tree
Configuring MISTP-PVST+ or MISTP on the Switch
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. The ports with lower port costs are more likely to be
chosen 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 of cost is from
1–65535 when using the short method for calculating port cost and from 1–200000000 when using the
long method. The default cost differs for different media. For information about calculating path cost,
see the
“Calculating and Assigning Port Costs” section on page 7-4
.
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
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
Task
Command
Step 1
Configure the MISTP port cost for a switch port.
set spantree portcost
mod/port cost
Step 2
Verify the port cost setting.
show spantree
mistp-instance
instance
[
mod/port
]
active