Cisco Systems 3750E manual Configuring Vlan Load Balancing on Flex Links, 21-8

Chapter 21 Configuring Flex Links and the MAC Address-Table Move Update Feature

Configuring Flex Links and MAC Address-Table Move Update

Configuring VLAN Load Balancing on Flex Links

Beginning in privileged EXEC mode, follow these steps to configure VLAN load balancing on Flex Links:

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify the interface, and enter interface configuration
		mode. The interface can be a physical Layer 2 interface or
		a port channel (logical interface). The port-channel range
		is 1 to 48.
Step 3 switchport backup interface interface-idprefer vlan		Configure a physical Layer 2 interface (or port channel)
	vlan-id	as part of a Flex Links pair with the interface. When one
		link is forwarding traffic, the other interface is in standby
		mode.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show interfaces [interface-id]switchport backup	Verify the configuration.
Step 6
	copy running-config startup config	(Optional) Save your entries in the switch startup
		configuration file.

In the following example, VLANs 1 to 50, 60, and 100 to 120 are configured on the switch:

Switch(config)#interface gigabitEthernet 2/0/6

Switch(config-if)#switchport backup interface gigabitEthernet 2/0/8 prefer vlan 60,100-120

When both interfaces are up, Gi2/0/8 forwards traffic for VLANs 60 and 100 to 120 and Gi2/0/6 forwards traffic for VLANs 1 to 50.

Switch#show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface Backup Interface State

------------------------------------------------------------------------

GigabitEthernet2/0/6			GigabitEthernet2/0/8			Active Up/Backup Standby
Vlans	Preferred on	Active		Interface:	1-50
Vlans	Preferred on	Backup		Interface:	60, 100-120

When a Flex Link interface goes down (LINK_DOWN), VLANs preferred on this interface are moved to the peer interface of the Flex Link pair. In this example, if interface Gi2/0/6 goes down, Gi2/0/8 carries all VLANs of the Flex Link pair.

Switch#show interfaces switchport backup

Switch Backup Interface Pairs:

Active Interface Backup Interface State

------------------------------------------------------------------------

GigabitEthernet2/0/6			GigabitEthernet2/0/8			Active Down/Backup Up
Vlans	Preferred on	Active		Interface:	1-50
Vlans	Preferred on	Backup		Interface:	60, 100-120

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

21-8 OL-9775-02