Moving onto EtherChannel technologies. EtherChannel is the Cisco terminology for what is elsewhere regarded as link aggregation or LAG. It’s the process of taking multiple physical ports, and combining them into what the switches sees as a single logical port. This has many benefits, which we’ll go through in this post. If you were just to connect multiple physical connections between 2 switches, spanning tree would be working hard to determine the loops and block ports. However with etherchannel as the switch only sees it as one logical connection, spanning tree does too! Loop free. Not only does multiple links increase bandwidth (doesn’t increase speed as each port still has a limit whether that be 100Mb, 1Gb, 10Gb etc) but it also provides redundancy. If one of the links fails in the etherchannel, the link as a whole will still work, just with a port less worth of bandwidth available. It will also automatically split the load between all links based on the results of a hashing algorithm, which we’ll discuss in a further post.
There are 3 different methods for configuring an etherchannel – 2 of these are protocols, and one is manual/static. Both the protocols offer advantages over the static method. They monitor and alert of any misconfigurations and can dynamically generate port channels. The first of these protocols is LACP (link aggregation control protocol.) It’s the industry standard protocol so is supported by all vendors. LACP will negotiate the etherchannel for you, by configuring each end with a ‘channel group mode.’ There are 2 options: active and passive.