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MAC Flaps on Ports to WLC

All, got some MAC Flapping errors below on our Core switch -

%SW_MATM-4-MACFLAP_NOTIF: Host in vlan 1 is flapping between port Gi1/0/4 and port Gi2/0/16

I get the same error for different MACs / VLAN but always the same 2 ports - Gi1/0/4 and Gi2/0/16.

These two ports connect back to our WLC 5505.

Any ideas on why the WLC links are showing MAC Flaps?

CDP from the core shows the WLC ports used.

WLC-01    Gig 1/0/4         177               H    AIR-CT550 LAGInterface0/3/1

WLC--01    Gig 2/0/16        177               H    AIR-CT550 Gig 0/0/2



Re: MAC Flaps on Ports to WLC

Can you check to ensure you have LAG enabled on the WLC?

Also, can you check the switch to ensure ports Gi1/0/4 and Gi2/0/16 are part of the same Port channel group?

Possibly post configs of the switch interfaces and the portchannel interface.

Sounds to me like a portchannel is not forming between the switch and the WLC so the switch is recieving frames with the same source MAC from both interfaces and it can't handle this if they are not part of a portchannel.


MAC Flaps on Ports to WLC


The ports on the Core (Gi1/0/4) and (Gi2/0/16) are not in any sort of Port Channel They are just acting as individual ports.
I assume they should form an etherchannel. This is fine, I can configure this.

On the WLC itself - how can i check if the ports are enabled for LAG. Commands seem to be a bit different on the WLC IOS.


New Member

MAC Flaps on Ports to WLC

HI ,

Please issue the command show interface summary and see the interface is in LAG mode or not .


Interface Name        Port  Vlan Id   IP Address       Type     Ap Mgr

--------------------  ----  --------  ---------------  -------  ------

ap-manager            LAG   15        x.x.x.x           Static   Yes

It says the port is in LAG or not    


MAC Flaps on Ports to WLC

Hi There,

So running command shows

x                  LAG  471      x.x.x.x     Dynamic No     No                                   

y                  LAG  472      x.x.x.x   Dynamic No     No                                   

z                  LAG  473      x.x.x.x     Dynamic No     No                                   

management                       LAG  untagged x.x.x.x    Static  Yes    No                                   

redundancy-management            LAG  untagged         Static  No     No                                   

redundancy-port                  -    untagged         Static  No     No                                   

service-port                     N/A  N/A     Static  No     No                                   

virtual                          N/A  N/A         Static  No     No   

Although I'm not sure which of these corresponds to the WLC ports -


AIR-CT550 Gig 0/0/2

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