flapping log on switch (port connect to WirelessAP)

Unanswered Question
Oct 20th, 2009

Hi,

I saw a lot of these logs on a Catalyst switch.

Gi0/9 and Gi0/11 of this switch are connected to Wireless APs(AP1 and AP2).

Oct 8 12:09:04.282 JST: %SW_MATM-4-MACFLAP_NOTIF: Host 00xx.xxxx.xxxx in

vlan 233 is flapping between port Gi0/9 and port Gi0/11

Oct 8 12:18:36.184 JST: %SW_MATM-4-MACFLAP_NOTIF: Host 00xx.xxxx.xxxx in

vlan 233 is flapping between port Gi0/9 and port Gi0/11

Oct 8 12:26:38.158 JST: %SW_MATM-4-MACFLAP_NOTIF: Host 00xx.xxxx.xxxx in

vlan 233 is flapping between port Gi0/11 and port Gi0/9

Oct 8 14:40:34.000 JST: %SW_MATM-4-MACFLAP_NOTIF: Host 00xx.xxxx.xxxx in

vlan 233 is flapping between port Gi0/9 and port Gi0/11

PC(00xx.xxxx.xxxx) is located near AP1 and AP2.

Do these logs appear when these events below happens?

-This PC try to connect to AP1 , failed, then try to connect to AP2.

-The user uses this PC near AP1, then move to near AP2, then move to near AP1.

Does anyone know what causes these logs?

Does this flapping log appear when only one time Host(00xx.xxxx.xxxx) flapping?

or when flapping count go over threshold value?

(I'm sorry for my poor English.)

I have this problem too.
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rduke Tue, 10/20/2009 - 06:17

Others may disagree, but personally I don't think it is a problem. I used to see this occasionally with wireless devices that are roaming between autonoumous APs. Sometimes a wireless device will roam to an AP on another switch, and you will see the flap on a trunk. WPA2 devices are supposed to preauthenicate to the next AP before they roam I believe, so the hand off of the mac to the next AP may not be completely instant resulting in the mac-flap messages. If you only have this occassionally on wireless devices, I would not worry about it. If you see this on LAN attached devices you should investigate. You should not see this with controller based APs since the traffic is tunneled to the controller.

Randy

masudaakiko Wed, 10/21/2009 - 03:39

Thank you for your reply.

I relieved. Maybe it's no problem because this log appeared only on wireless devices.

When mac-address-aging-time (default:300s) passed , does this log stop appearing?

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