Load Sharing Using Stp Path Cost - Cisco WS-C2955T-12 Software Manual

Load Sharing Using STP
Command
Step 16 interface fa0/1
Step 17 spanning-tree vlan 8 9 10
port-priority 10
Step 18 end
Step 19
interface fa0/2
Step 20
spanning-tree vlan 3 4 5 6 port
priority 10
Step 21
exit
Step 22
show running-config

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. The VLANs keep the traffic separate; because
no loops exist, STP does not disable the ports; and redundancy is maintained in the event of a lost link.
In Figure
follows:
•
•
•
•
Figure 8-6
VLANs 2 – 4 (path cost 30)
VLANs 8 – 10 (path cost 19)
Catalyst 2900 Series XL and Catalyst 3500 Series XL Software Configuration Guide
8-34
Purpose
Enter interface configuration mode, and define the interface to set the STP
port priority.
Assign the port priority of 10 for VLANs 8, 9, and 10.
Return to global configuration mode.
Enter interface configuration mode, and define the interface to set the STP
port priority.
Assign the port priority of 10 for VLANs 3, 4, 5, and 6.
Return to privileged EXEC mode.
Verify your entries.
8-6, trunk ports 1 and 2 are 100BASE-T ports. The path costs for the VLANs are assigned as
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.
Load-Sharing Trunks with Traffic Distributed by Path Cost
Trunk port 1
Switch 2
Switch 1
Trunk port 2
VLANs 8 – 10 (path cost 30)
VLANs 2 – 4 (path cost 19)
Chapter 8 Configuring VLANs
78-6511-08