Cisco Systems 3750E manual Configuring Layer 2 EtherChannels, 37-13

Chapter 37 Configuring EtherChannels and Link-State Tracking

Configuring EtherChannels

–An EtherChannel supports the same allowed range of VLANs on all the ports in a trunking Layer 2 EtherChannel. If the allowed range of VLANs is not the same, the ports do not form an EtherChannel even when PAgP is set to the auto or desirable mode.

–Ports with different spanning-tree path costs can form an EtherChannel if they are otherwise compatibly configured. Setting different spanning-tree path costs does not, by itself, make ports incompatible for the formation of an EtherChannel.

•For Layer 3 EtherChannels, assign the Layer 3 address to the port-channel logical interface, not to the physical ports in the channel.

•For cross-stack EtherChannel configurations, ensure that all ports targeted for the EtherChannel are either configured for LACP or are manually configured to be in the channel group using the channel-groupchannel-group-numbermode on interface configuration command. The PAgP protocol is not supported on cross- stack EtherChannels.

•If cross-stack EtherChannel is configured and the switch stack partitions, loops and forwarding misbehaviors can occur.

Configuring Layer 2 EtherChannels

You configure Layer 2 EtherChannels by assigning ports to a channel group with the channel-groupinterface configuration command. This command automatically creates the port-channel logical interface.

If you enabled PAgP on a port in the auto or desirable mode, you must reconfigure it for either the on mode or the LACP mode before adding this port to a cross-stack EtherChannel. PAgP does not support cross-stack EtherChannels.

Beginning in privileged EXEC mode, follow these steps to assign a Layer 2 Ethernet port to a Layer 2 EtherChannel. This procedure is required.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify a physical port, and enter interface configuration mode.
		Valid interfaces include physical ports.
		For a PAgP EtherChannel, you can configure up to eight ports of
		the same type and speed for the same group.
		For a LACP EtherChannel, you can configure up to 16 Ethernet
		ports of the same type. Up to eight ports can be active, and up to
		eight ports can be in standby mode.
Step 3
	switchport mode {access trunk}	Assign all ports as static-access ports in the same VLAN, or
	switchport access vlan vlan-id	configure them as trunks.
		If you configure the port as a static-access port, assign it to only
		one VLAN. The range is 1 to 4094.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		37-13