Etherchannel and Interface Teaming Question

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May 27th, 2009
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Hi - We have an HP server with an A/A teaming configuration that serves up DHCP. The two interfaces are connected to a 4506 with port channel assignments, but I see that they left the channel-group mode as "desirable" on both interfaces, instead of "on", and so the Etherchannel does not come up. Can anyone tell me how this really affects switch traffic, because general network perfomance is mediocre. If two separate MAC's are responding for one IP address, I would think it would be bad. - Thnx Dave

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Giuseppe Larosa Wed, 05/27/2009 - 07:50
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Hello Dave,

the best choice is to use an LACP negotiated bundle.

you can configure in active mode on the switch side.

Server people has to configure it for LACP or the ports are placed down if the switch doesn't here LACP frames (every 30 seconds reaction after 90 seconds of no lacp frames received)


see


http://www.cisco.com/en/US/tech/tk389/tk213/technologies_configuration_example09186a008089a821.shtml


Hope to help

Giuseppe




prakkdangc Wed, 05/27/2009 - 08:35
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Thanks Giuseppe. Unfortunately we standardize on Etherchannel configurations, so what I really want to know is what the effect will be if the the port channel is not up, when the teaming configuration is active/active. I am remote and not able to capture any information, but I think this misconfiguration is causing traffic problems as it is. - Dave

Giuseppe Larosa Wed, 05/27/2009 - 09:09
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Hello Dave,

we reviewed the policy on how to configure etherchannels in our server farms.


First attempts to use LACP were not successful but now we are getting good results.


if the port channel is not configured on the switch side or it is waiting for a successful PAGP negotiation (that is Cisco proprietary this is the key point here) to complete you will get a lot of errors like


host with MAC x flapping between ports Y and Z


or you configure the ports to be bundle without negotiation with on mode or you move to LACP


Hope to help

Giuseppe


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