Any practical use of etherchannel these days?

fmitawaps

I'm going through some of my CCNA training videos, and there was a brief section on etherchannel.

It was interesting to see how it was done, but it seems like any decent layer 3 switch with even a basic fiber connection or gigabit ethernet port could do it better and with less fuss.

Maybe on an old network switch with nothing better than 10/100 ports it could be useful to increase switch-to-switch bandwidth.

Does anyone administer or configure networks and use etherchannel these days?

Iristheangel

Pretty much every network I've ever seen or worked on

OctalDump

The other thing which etherchannel allows, besides bandwidth aggregation, is redundancy. It's the redundancy that's the big plus in networks. Instead of a situation where you have STP running, multiple connections between switches and STP shuts the redundant links down, with Etherchannels you can have the multiple links all active at the same time.

You can etherchannel larger pipes as well, so you might bond multiple gigabit connections or multiple 10Gbe or 40Gb channels. The fatter links might be at the core, or could be supporting consolidated datacentre with FCoE or other very bandwidth hungry applications. You might be surprised how much bandwidth you can actually use.

networker050184

I say no. There is no place for ether channel in modern networks. Layer 3 ecmp is the way to go for sure. The only part that's hard to get away from is dual attached servers with mlag.

pevangel

I've used port aggregation twice recently for different purposes. One was for 20G last mile to a customer's HQ. The other setup was lacp link protection for redundancy on a switch with dual switching/control modules.

fmitawaps

When I did my etherchannel lab on my real equipment tonight (I have 3 3560 switches and 3 2811 routers), I plugged 3 crossover Ethernet cables into the same 3 ports on each of 2 switches, and I watched the port lights change color and end up with 4 green and 2 orange as it set itself up on spanning tree.

Once I shut down the ports, configured etherchannel, and brought them back up, I had 6 greens on the port lights, and from what the training video said, the switches see those 3 ethernet cables as one link between 2 switches.

So on any switch, you can have etherchannel OR STP? Or can STP and etherchannel be running on the same switches?

For example, maybe switches 1, 2, and 3 are set up on STP, but switches 3 and 4 have etherchannel running between them?

Iristheangel

STP still runs on port-channels and the switch itself. STP just sees the aggregated ports as one single link as opposed to blocking multiple links.

OctalDump

fmitawaps wrote: »

When I did my etherchannel lab on my real equipment tonight (I have 3 3560 switches and 3 2811 routers), I plugged 3 crossover Ethernet cables into the same 3 ports on each of 2 switches, and I watched the port lights change color and end up with 4 green and 2 orange as it set itself up on spanning tree.

Once I shut down the ports, configured etherchannel, and brought them back up, I had 6 greens on the port lights, and from what the training video said, the switches see those 3 ethernet cables as one link between 2 switches.

So on any switch, you can have etherchannel OR STP? Or can STP and etherchannel be running on the same switches?

For example, maybe switches 1, 2, and 3 are set up on STP, but switches 3 and 4 have etherchannel running between them?

Yeah, sorry. I didn't mean to make it seem like an either/or situation. Spanning tree will treat an etherchannel as though it is a single link.

Think of it in the most basic sense. Two switches with two cables connecting them. Without etherchannel, and just STP, then one cable is active and the other is not in use - "in reserve" - if the active link fails (port shutdown, cable faulty or unplugged, whatever), then it fails over to the other cable. Which ever way, you only have the bandwidth of one link. With etherchannel, then both cables are in use at the same time, if one cable fails, then the etherchannel is still active but with just one cable. Spanning tree will still be active, but it sees the etherchannel as one link.

If you wanted you could set up two separate etherchannels between the two switches, and you would see that only one is active, since the other is turned off by STP.

So your choices are basically redundant links in a fail over situation OR redundant links with fail over and load balancing.

pinkiaiii

To answer in short most small to medium sized places would be ok on stp with one redundant link,but anything past that ISP large corporations,data centers would allocate wast amounts of switches for ether channels so while in single floor building it wouldnt be necessary but along the way your ISP or even larger tier ISPs would have many of those to maintain redundancy if one of links failed.

james43026

networker050184 wrote: »

I say no. There is no place for ether channel in modern networks. Layer 3 ecmp is the way to go for sure. The only part that's hard to get away from is dual attached servers with mlag.

Interesting, are you saying that a layer 2 switch, can use ECMP? I don't think so. ECMP is a layer 3 concept, and is already employed by both OSPF and EIGRP, with EIGRP also able to do unequal ECMP. Etherchannel is a layer 2 concept, and is still used for redundancy and bandwidth aggregation in any layer 2 environment.

OctalDump

james43026 wrote: »

Interesting, are you saying that a layer 2 switch, can use ECMP? I don't think so. ECMP is a layer 3 concept, and is already employed by both OSPF and EIGRP, with EIGRP also able to do unequal ECMP. Etherchannel is a layer 2 concept, and is still used for redundancy and bandwidth aggregation in any layer 2 environment.

Maybe networker050184 is lucky enough to work with somewhere that has only layer 3 switches.

networker050184

james43026 wrote: »

Interesting, are you saying that a layer 2 switch, can use ECMP? I don't think so. ECMP is a layer 3 concept, and is already employed by both OSPF and EIGRP, with EIGRP also able to do unequal ECMP. Etherchannel is a layer 2 concept, and is still used for redundancy and bandwidth aggregation in any layer 2 environment.

I'd be more looking to go L3 with overlay rather than building out L2 networks if you need L2 connectivity past the access switch (which you shouldn't in 99% of circumstances). Of course keep it simple in smaller networks so you may still be deploying small scale flat L2 networks there. These days really you can get L3 switching to your closet/TOR for fairly cheap with the growth of merchant silicon in the field. VXLAN is your friend.

james43026

networker050184 wrote: »

I'd be more looking to go L3 with overlay rather than building out L2 networks if you need L2 connectivity past the access switch (which you shouldn't in 99% of circumstances). Of course keep it simple in smaller networks so you may still be deploying small scale flat L2 networks there. These days really you can get L3 switching to your closet/TOR for fairly cheap with the growth of merchant silicon in the field. VXLAN is your friend.

Ahhh okay. I see what you are saying. I'll take it your work environment doesn't use end to end vlans, and you stick with local vlans?

networker050184

Yes L3 everywhere when possible. Any disparate L2 connectivity needs use VXLAN, MPLS or a combination of both.

Now, keep in mind this is for a "modern" network being built today for this discussion. Very rarely do you get to just build a whole new network from scratch though so cleaning up VLANs spanned around on older networks is not always an easy, or cheap task!

fmitawaps

Etherchannel question. I re-watched my training video for this, but it did not specifically state what I was looking for.

Say you have etherchannel set up on 2 switches, 3 ports in each. Say it is on ports 22, 23, and 24. Does the ethernet cable from port 22 of one switch HAVE TO plug into port 22 on the other switch? And the same for the others, port 23 to port 23, port 24 to port 24, etc?

Or does that not matter, and ports 22, 23, and 24 of one switch can connect to any one of ports 22, 23, and 24 on the other switch?

My guess is that since etherchannel claims to see it all as one link, that it would not matter which ports were plugged into whatever other port.

networker050184

No the port number doesn't matter. Whether it is static or using a negotiation protocol nothing about port is needed to match for functionality.

shortstop20

Port channels have many uses. We use them for devices which require >1Gbps but <10Gbps, just one example.

theodoxa

1) Etherchannel allows you to increase bandwidth without having to buy new switches. They can be used to bridge the gap until you are able to buy new equipment.

2) Etherchannel provides redundancy. If one link fails, traffic can still flow.

3) Fast Ethernet (100 Mbps) isn't the only speed link that can be used in an Etherchannel. You can group faster links.

james43026

networker050184 wrote: »

Yes L3 everywhere when possible. Any disparate L2 connectivity needs use VXLAN, MPLS or a combination of both.

Now, keep in mind this is for a "modern" network being built today for this discussion. Very rarely do you get to just build a whole new network from scratch though so cleaning up VLANs spanned around on older networks is not always an easy, or cheap task!

I never really thought of implementing VXLAN outside of a datacenter / VM farm. Although I've never configured it, I just know a bit about it. Like what would you use to move VXLAN data around the IP network if you weren't using a VM? I'm only aware of using things like NVGRE, virtual switches, and other hypervisor related technologies in order to create the tunneling involved.