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Catalyst 2960 and 2960-S Switch Software Configuration Guide
OL-8603-09
Chapter 13 Configuring VLANs
Configuring VLAN Trunks
Load Sharing Using STP Path Cost
You can configure parallel trunks to share VLAN traffic by setting different path costs on a trunk and
associating the path costs with different sets of VLANs, blocking different ports for different VLANs.
The VLANs keep the traffic separate and maintain redundancy in the event of a lost link.
In Figure 13-3, Trunk ports 1 and 2 are configured as 100BASE-T ports. These VLAN path costs are
assigned:
• VLANs 2 through 4 are assigned a path cost of 30 on Trunk port 1.
• VLANs 8 through 10 retain the default 100BASE-T path cost on Trunk port 1 of 19.
• VLANs 8 through 10 are assigned a path cost of 30 on Trunk port 2.
• VLANs 2 through 4 retain the default 100BASE-T path cost on Trunk port 2 of 19.
Figure 13-3 Load-Sharing Trunks with Traffic Distributed by Path Cost
Step 12
Repeat Steps 7 through 10 on Switch A for a second port in the switch
stack.
Step 13
Repeat Steps 7 through 10 on Switch B to configure the trunk ports
that connect to the trunk ports configured on Switch A.
Step 14
show vlan When the trunk links come up, VTP passes the VTP and VLAN
information to Switch B. Verify that Switch B has learned the VLAN
configuration.
Step 15
configure terminal Enter global configuration mode on Switch A.
Step 16
interface interface-id_1 Define the interface to set the STP port priority, and enter interface
configuration mode.
Step 17
spanning-tree vlan 8-10 port-priority 16 Assign the port priority of 16 for VLANs 8 through 10.
Step 18
exit Return to global configuration mode.
Step 19
interface interface-id_2 Define the interface to set the STP port priority, and enter interface
configuration mode.
Step 20
spanning-tree vlan 3-6 port-priority 16 Assign the port priority of 16 for VLANs 3 through 6.
Step 21
end Return to privileged EXEC mode.
Step 22
show running-config Verify your entries.
Step 23
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
90573
Switch A
Switch B
Trunk port 1
VLANs 2 – 4 (path cost 30)
VLANs 8 – 10 (path cost 19)
Trunk port 2
VLANs 8 – 10 (path cost 30)
VLANs 2 – 4 (path cost 19)