EtherChannel and Port Channel
August 15, 2013 2 Comments
In the networking world, you’ve no doubt heard the terms EtherChannel, port channel, LAG, MLAG, etc. These of course refer to taking multiple Ethernet connections and treating them as a single link. But one of the more confusing aspects I’ve run into is what’s the difference, if any, between the term EtherChannel and port channel? Well, I’m here to break it down for you.
OK, not that kind of break-it-down
First, let’s talk about what is vendor-neutral and what is Cisco trademark. EtherChannel is a Cisco trademarked term (I’m not sure if port channel is), while the vendor neutral term is LAG (Link Aggregation). Colloquially, however, I’ve seen both Cisco terms used with non-Cisco gear. For instance: “Let’s setup an Etherchannel between the Arista switch and the Juniper switch”. It’s kind of like in the UK using the term “hoovering” when the vacuum cleaner says Dyson on the side.
So what’s the difference between EtherChannel and port channel? That’s a good question. I used to think that EtherChannel was the name of the technology, and port channel was a single instance of that technology. But in researching the terms, it’s a bit more complicated than that.
Both Etherchannel and port channel appear in early Cisco documentation, such as this CatOS configuration guide. (Remember configuring switches with the “set” command?) In that document, it seems that port channel was used as the name of the individual instance of Etherchannel, just as I had assumed.
I love it when I’m right
And that seems to hold true in this fairly recent document on Catalyst IOS 15, where EtherChannel is the technology and port channel is the individual instance.
But wait… in this older CatOS configuration guide, it explicitly states:
This document uses the term “EtherChannel” to refer to GEC (Gigabit EtherChannel), FEC (Fast EtherChannel), port channel, channel, and port group.
So it’s a bit murkier than I thought. And that’s just the IOS world. In the Nexus world, EtherChannel as a term seems to be falling out of favor.
Take a look at this Nexus 5000 CLI configuration guide for NXOS 4.0, and you see they use the term EtherChannel. By NX-OS 5.2, the term seems to have changed to just port channel. In the great book NX-OS and Cisco Nexus Switching, port-channel is used as the term almost exclusively. EtherChannel is mentioned once that I can see.
So in the IOS world, it seems that EtherChannel is the technology, and port channel is the interface. In the Nexus world, port channel is used as the term for the technology and the individual interface, though sometimes EtherChannel is referenced.
It’s likely that port channel is preferred in the Nexus world because NX-OS is an offspring of SANOS, which Cisco initially developed for the MDS line of Fibre Channel switches. Bundling Fibre Channels ports on Cisco switches isn’t called EtherChannels, since those interfaces aren’t, well, Ethernet. The Fibre Channel bundling technology is instead called a SAN port channel. The command on a Nexus switch to look at a port cchannel is “show port-channel”, while on IOS switches its “show etherchannel”.
When a dual-homed technology was developed on the Nexus platform, it was called vPC (Virtual Port Channel) instead of VEC (Virtual EtherChannel).
Another interesting aspect to this discussion is that EtherChannel is capitalized as a proper noun, while port channel is not. In the IOS world, it’s EtherChannel, though when its even mentioned in the Nexus world, it’s sometimes Etherchannel, without the capital “C”. Port channel is written often as port channel or port-channel (the later is used almost exclusively in the NX-OS book).
So where does that leave the discussion? Well, I think in very general terms, if you’re talking about Cisco technology, Etherchannel, EtherChannel, port channel, port channel, and LAG are all acceptable term for the same concept. When discussing IOS, it’s probably more correct to use the term Etherchannel. When discussing NX-OS, port channel. But again, either way would work.