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Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
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Chapter 8 Configuring Spanning Tree
Using MISTP-PVST+ or MISTP
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 cost is from 1 to
65535 when using the short method for calculating port cost and from 1 to 200000000 when using the
long method. The default cost differs for different media. For information about calculating port cost,
see the
“Calculating and Assigning Port Costs” section on page 8-4
.
To configure the port cost for a port, perform this task in privileged mode:
This example shows how to configure the port cost on a MISTP instance and verify the configuration:
Console> (enable)
set spantree portcost 2/12 22222222
Spantree port 2/12 path cost set to 22222222.
Console> (enable)
show spantree mistp-instance active
Instance 1
Spanning tree mode MISTP-PVST+
Spanning tree type ieee
Spanning tree instance enabled
Designated Root 00-d0-00-4c-18-00
Designated Root Priority 32769 (root priority: 32768, sys ID ext: 1)
Designated Root Cost 0
Designated Root Port none
VLANs mapped: 6
Root Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
Bridge ID MAC ADDR 00-d0-00-4c-18-00
Bridge ID Priority 32769 (bridge priority: 32768, sys ID ext: 1)
VLANs mapped: 6
Bridge Max Age 20 sec Hello Time 2 sec Forward Delay 15 sec
Port Inst Port-State Cost Prio Portfast Channel_id
------------------------ ---- ------------- --------- ---- -------- ----------
2/12 1 forwarding 22222222 40 disabled 0
Console> (enable)
Configuring the MISTP Port Priority
You can configure the port priority of ports. The port with the lowest priority value forwards frames for
all VLANs. The possible port priority value is 0–63; the default is 32. If all ports have the same priority
value, the port with the lowest port number forwards frames.
To configure the port priority for a port, perform this task in privileged mode:
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
Task
Command
Step 1
Configure the MISTP port priority for a port.
set spantree portpri
mod/port
priority
[
instance
]
Step 2
Verify the port priority setting.
show spantree
mistp-instance
instance
[
mod/port
]
active