Cisco Etherchannel

Posted on 2007-10-07
Medium Priority
Last Modified: 2012-07-17

When configuring Etherchannel between 2 3750 devices which protocol and mode should I use?
Question by:Ciderspine
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Accepted Solution

Don Johnston earned 680 total points
ID: 20031258
PAgP or LACP. As long as you use the same protocol on each end, they're both about the same.

I'm partial to PAgP in Desirable mode.
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JFrederick29 earned 660 total points
ID: 20031283
I myself get paranoid about "negotiation" so I always set it to "on" on both ends.
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Expert Comment

by:Don Johnston
ID: 20031291
I agree about negotiation... Except here. The problem with "on" where etherchannel is concerned is that if there's a problem, "on" may not errdisable the ports. Then you've got yourself a good old fashioned broadcast storm. Desirable mode is better at dealing with this.
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Assisted Solution

grsteed earned 660 total points
ID: 20031465
I've also seen the problem that donjohnston mentions with "on" mode in PAgP, so now I use "desirable"  

I also had one recently where the link (between a 6913 and an HP Blade Chassis w/built-in Cisco switches, 3020?) where the links set for desirable wouldn't come up because they were errdisabled by udld. A check of another working chassis showed that udld wasn't enabled. When I set it to disable, the links came up.

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Expert Comment

by:Don Johnston
ID: 20031766
Yep. That's what I tell people in class: With etherchannel, EVERYTHING must match. :-)

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