Configuring The Pvst+ Port Cost For A Vlan; Configuring The Pvst+ Port Priority For A Vlan - Cisco WS-C6506 Software Manual

Chapter 7 Configuring Spanning Tree

Configuring the PVST+ Port Cost for a VLAN

You can configure the port cost for a port on a per-VLAN basis. Ports with a lower port cost in the VLAN
are more likely to be chosen to forward frames. You should 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 1–65535 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 port cost, see the
To configure the PVST+ port VLAN cost for a port, perform this task in privileged mode:
Task
Configure the PVST+ port cost for a
VLAN on a port.
When you use the set spantree channelcost command, it does not appear in the configuration file. The
Note
command causes a "set spantree portcost" entry to be created for each port in the channel. See the
"Setting the EtherChannel Port Path Cost"
information on using the set spantree channelcost command.
This example shows how to configure the PVST+ port VLAN cost on port 2/3 for VLANs 1–5:
Console> (enable) set spantree portvlancost 2/3 cost 20000 1-5
Port 2/3 VLANs 6-11,13-1005,1025-4094 have path cost 12.
Port 2/3 VLANs 1-5,12 have path cost 20000.
This parameter applies to trunking ports only.
Console> (enable)

Configuring the PVST+ Port Priority for a VLAN

When the switch is in PVST+ mode, you can set the port priority for a trunking port in a VLAN. The
port with the lowest priority value for a specific VLAN forwards frames for that VLAN. The possible
port priority value is a multiple of 16 from 0–240. The default is 16. If all ports have the same priority
value for a particular VLAN, the port with the lowest port number forwards frames for that VLAN.
The port VLAN priority value must be lower than the port priority value.
To configure the port VLAN priority for a port, perform this task in privileged mode:
Task
Step 1
Configure the PVST+ port priority for a VLAN on
a port.
Step 2 Verify the port VLAN priority.
This example shows how to configure the port priority for VLAN 6 on port 2/3:
Console> (enable) set spantree portvlanpri 2/3 16 6
Port 2/3 vlans 6 using portpri 16.
Port 2/3 vlans 1-5,7-800,802-1004,1006-4094 using portpri 32.
Port 2/3 vlans 801,1005 using portpri 4.
This parameter applies to trunking ports only.
OL-8978-04
"Calculating and Assigning Port Costs" section on page
Command
set spantree portvlancost {mod/port} [cost cost]
[vlan_list]
section in Chapter 6, "Configuring EtherChannel,"
Command
set spantree portvlanpri mod/port priority
[vlans]
show config all
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
Configuring PVST+ on the Switch
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for
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