Configuring EtherChannel with LACP is based on two steps:

Step 1. Specify the interfaces that compose the EtherChannel group using the interface range interface global configuration mode command. The range keyword allows you to select several interfaces and configure them all together. A good practice is to start by shutting down those interfaces, so that any incomplete configuration does not create activity on the link.

Step 2. Create the port channel interface with the channel-group identifier mode active command in interface range configuration mode. The identifier specifies a channel group number. The mode active keywords identify this as an LACP EtherChannel configuration.

Note: EtherChannel is disabled by default.

In Figure 1, FastEthernet0/1 and FastEthernet0/2 are bundled into EtherChannel interface port channel 1.

To change Layer 2 settings on the port channel interface, enter port channel interface configuration mode using the interface port-channel command, followed by the interface identifier. In the example, the EtherChannel is configured as a trunk interface with allowed VLANs specified. Also shown in Figure 1, interface port channel 1 is configured as a trunk with allowed VLANs 1, 2, and 20.

Use the Syntax Checker in Figure 2 to configure EtherChannel on switch S1.