Cisco Systems 3750E manual Load Sharing Using STP Path Cost, Or switch stack, 13-26

Chapter 13 Configuring VLANs

Configuring VLAN Trunks

	Command	Purpose
Step 13
		Repeat Steps 7 through 11on Switch A for a second port in the switch
		or switch stack.
Step 14
		Repeat Steps 7 through 11on Switch B to configure the trunk ports that
		connect to the trunk ports configured on Switch A.
Step 15
	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 16
	configure terminal	Enter global configuration mode on Switch A.
Step 17
	interface gigabitethernet1/ 0/1	Define the interface to set the STP port priority, and enter interface
		configuration mode.
Step 18
	spanning-tree vlan 8-10 port-priority 16	Assign the port priority of 16 for VLANs 8 through 10.
Step 19
	exit	Return to global configuration mode.
Step 20
	interface gigabitethernet1/0/2	Define the interface to set the STP port priority, and enter interface
		configuration mode.
Step 21
	spanning-tree vlan 3-6 port-priority 16	Assign the port priority of 16 for VLANs 3 through 6.
Step 22
	end	Return to privileged EXEC mode.
Step 23
	show running-config	Verify your entries.
Step 24
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

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 13-4, 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.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
13-26	OL-9775-02