Using EtherChannel for Cisco Networking

Part of the Cisco Networking All-in-One For Dummies Cheat Sheet

Don't be afraid to use EtherChannel on your Cisco network. EtherChannel allows you to take up to eight network ports on your switch and treat them as a single larger link. This can be used to connect servers with multiple network cards that are bonded (or teamed) to a switch, or to connect multiple switches together. There are two main negotiation protocols, Port Aggregation Protocol (PAgP) which is a proprietary Cisco protocol and Link Aggregation Control Protocol (LACP) which is an open standards protocol.

To set EtherChannel to use with of the protocols you will configure it to support one of the following modes.

  • auto: Sets the interface to respond to PAgP negotiation packets, but the interface will start negotiations on its own.

  • desireable: Sets the interface to actively attempt to negotiate a PAgP connection.

  • on: Forces the connection to bring all links up without using a protocol to negotiate connections. This mode can only connect to another device that is also set to on. When using this mode, the switch does not negotiate the link using either PAgP or LACP.

  • active: Sets the interface to actively attempt to negotiate connections with other LACP devices.

  • passive: Sets the interface to respond to LACP data if it receives negotiation requests from other systems.

The following example will configure EtherChannel to use group ports 11 and 12 on the switch together using PAgP as the protocol. The same type of command would be used on the switch to which Switch1 is connected.

Switch1> enable
Switch1# configure terminal 
Switch1(config)# interface range FastEthernet0/11 -12 
Switch1(config-if-range)# switchport mode access
Switch1(config-if-range)# switchport access vlan 10
Switch1(config-if-range)# channel-group 5 mode desirable
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