4402 wlc appears to switch to be flapping

Unanswered Question
Jul 26th, 2007
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I have both interfaces setup as lag, connected on different switch cards on the same switch.

In the switch logs, it is returning errors that the host is flapping. Is there something I have configured incorrectly, or is that expected behavior due to the LAG setup.

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Overall Rating: 4.5 (2 ratings)
ankbhasi Thu, 07/26/2007 - 05:56
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  • Cisco Employee,

Hi Friend,

Just want to make sure after you enabled LAG on controller, have you reloaded the controller once?

Also I believe you must be using Cisco SFP modules installed on your WLC?

Have you also configured etherchannel group on your switch and make sure both the ports have exactly same config.



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jarrodpicha Thu, 07/26/2007 - 07:10
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Yes, the controller has been restarted.

Yes, they are SFP modules.

No, I don't think an etherchannel group is setup with those two ports.

ankbhasi Thu, 07/26/2007 - 07:25
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  • Cisco Employee,

Hi Friend,

So there is the problem. If you do not have etherchannel configured on your switch side then it will create a loop and flapping message are very obvious in this case.

Configure the 2 ports as a part of sam channel group and it will resolve your issue.

Something like this


Switch(config-if)#channel-group mode on


Switch(config-if)#channel-group mode on

I have posted a config specific for etherchannel you interface can have other configs also like vlans and other stuff but make sure both the ports have same configs.



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