Why use PAgP or LACP

Futura

Proprierty PAgP or industry Standard LACP.

Why would you want to use any of these Etherchannel negotiation protocols when setting unconditional Etherchannel (Port-channel 1 mode on) will unconditionally etherchannel the links.

Any thoughts or suggestions or am I getting the wrong end of the stick here?

Thanks

srg

Try to put "mode on" and then connect the other side of the link to a regular non-portchannel port and see what happens..

PAgP and LACP ensures that you actually have a working port-channel on both sides and mitigates loops and faults that may occur when not using them and connecting your cables wrong.

malcybood

It's basically a way of ensuring your configuration is correct.

Similar to a port being configured as a 10/100/1000 auto negotiate as opposed to fixing it to 1Gbps.....

It will work if both ends are "on" but best practice is to specify a protocol to avoid instability and troubleshooting complexity. If your corporate policy is to use PAGP on etherchannels, then there is only going to be specific types of issues you can come across.

Likewise for LACP.

It's about consistent configuration and ease of support / troubleshooting to stick to one protocol.

There are obviously times when you may need to mix and match i.e. if your policy is PAGP, but you have a non Cisco switch that you want to create an etherchannel to you would use LACP.

Futura

Fair enough, but in my opinion setting it to channel mode on is less of a worry than using the protocols, simply setting mode to on at both ends means there is no negotiation, like setting Duplex Full etc, which confirms your are happy with the settings.

I will carry on using mode on for my configs, but will take these options into account for the Switch Exam.

Thanks for input.

Iristheangel

In a lab environment, it doesnt really matter but in the real world where you have hundreds of feet of cabling between both switches, its can cause all sorts of issues if its configured for on and plugged into the wrong port on another switch as well as harder to troubleshoot or diagnose when pagp or lacp are not being used. Even if you configure it right the first time, someone may move the wiring and then you have a loop among other issues because that port is configurd to come up and be a port-channel, no matter what. When in doubt or unsure, always follow best practices. If you were using an etherchannel protocol on both ends of the link and you plugged one side into the wrong port, its easier to diagnose port channel not forming.

Futura

Iristheangel wrote: »

hundreds of feet of cabling between both switches, its can cause all sorts of issues

Agreed! , The only Etherchannels set up I have at the moment are in the same comms room, so fair enough, Stretching over a large distance may cause issues.

Thanks

Iristheangel

Even if it's right there next to each other or even through a patch panel 5 feet away, I wouldn't recommend it. You never know when someone who doesn't understand your network design, a junior admin, or even an end user may make, ahem, "adjustments" without realizing they're about to majorly mess things up by moving it from one port to another. Always plan for the worst. It's a lot better to plan a little more out than to get that call in the middle of the night

networker050184

Agree with Iristheangel. I'd only use mode on if it were needed for some technical reason. No point in not using a protocol to properly negotiate if you can.

malcybood

Agree with the guys and gals above.

Being blunt, taking the easy option usually results in outages when it comes to networking.

Best to stick to best practice design in my opinion.