2 types of EtherChannels

EtherChannel is a pretty obvious technology which allows to bundle several physical ports into one thick logical port to archive more throughput and even ease configuration of redundancy and stuff.

One think which is not always obvious about EtherChannels is that they can be both Layer2 and Layer3 bundles.

L2 EtherChannel is a collection of switch ports which looks like a single L2 switching port (for example, from STP point of view). Here is a simple configuration:

interface FastEthernet1/0
channel-group 10 mode desirable
!
interface FastEthernet1/1
channel-group 10 mode desirable

L3 etherchannel is a bundle of no swithport ports that make up one fast routing port. The configuration procedure is a bit more tricky because a special port-channel (virtual port) needs to be created:

interface port-channel 1
ip address 192.168.1.1 255.255.255.0
!
interface FastEthernet1/0
no switchport
no ip address
channel-group 1 mode on
!
interface FastEthernet1/1
no switchport
no ip address
channel-group 1 mode on

Notice, that we also need to convert all participating ports to Layer3.