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Community Member

4 WLCs client MAC flapping

Hi all,

I've got a topology as on the diagram


All of the controllers have the same number of VLANs and are configured identically.

The management IPs of WLCs are,,, (vlan 100).

The VLAN with the most clients is vlan 99.

All of the controllers are in the same mobility group.

All of the controllers may act as mobility anchors.

There is totally about 70 APs.

There is usually about 2000 wireless clients.

The issue is the following: on both switches I get many (10-15 a second) MAC flapping messages on interfaces Gi0/2, Gi0/3 and the uplink to the neighbor switch with remote WLCs. The flapping MACs belong to wireless clients.

The AP placement is suboptimal, therefore client migration is happening all the time, even when clients aren't moving. MAC flapping is happeing during hand-offs. Before I started troubleshooting, the mobility wasn't configured at all and there were no anchors. I've changed that, now, with anchors, the issue persists.

Here is a sample output of debug mobility hand-offs on one of the WLCs ( with the flapping MAC:

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1 Mobility packet received from:

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1, port 16666

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1   type: 3(MobileAnnounce)  subtype: 0  version: 1  xid: 151692  seq: 62502  len 116 flags 0

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1   group id: 4e175c50 c39ec1ac d30a5cc7 f7eb6006

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1   mobile MAC: 20:13:e0:a3:31:d1, IP:, instance: 0

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1   VLAN IP:, netmask:

*mmListen: Oct 01 16:15:24.938: Switch IP:

*mmListen: Oct 01 16:15:24.938: Vlan List payload not found, ignoring ...

*mmListen: Oct 01 16:15:24.938: IP Address don't compare for client 20:13:e0:a3:31:d1 is 0

*mmListen: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1 Handoff SSID Mismatch, Local = , Request = XXX-public

    **** Handoff Request Ignored

*apfReceiveTask: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1 Mobile 20:13:e0:a3:31:d1 associated with another AP elsewhere, delete mobile

*apfReceiveTask: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1 START (0) mobility role update request from Unassociated to Handoff

  Peer =, Old Anchor =, New Anchor =

*apfReceiveTask: Oct 01 16:15:24.938: 20:13:e0:a3:31:d1 Mobility Response: IP code Handoff Indication (2), reason Client handoff successful - anchor retained (0), PEM State START, Role Handoff(6)

Anyone had similar issues?


Hall of Fame Super Silver

Re: 4 WLCs client MAC flapping

If your AP's are in a salt n pepper design, or if you using FlexConnect local switching, you can see this because the arp entries are still valid until the arp cache times out. This was seen in autonomous installs back in the days and was normal.

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Community Member

Re: 4 WLCs client MAC flapping

Thanks Scott!

I'll change the physical design and implement STP, so both controllers share a single link to the switch.

VIP Purple

Re: 4 WLCs client MAC flapping

Hi Tim,

I would suggest the followings to consider

1. Make sure geographically closeby APs always register to a particular 4402 as primary. In this way 80-90% of your user roaming should be intra-controller & should not have this issue. Similary those AP should have another single controller as secondary to have predictive fail-over & roaming won't be having similar issues even your primary controller down.

2. In case, if there is inter-controller roaming, do it as much as L2 (since you have same L2 network across 4 controllers) since your topology supports that. (ie given wlan interface should have same subnet IP in all 4 controllers)

3. Check output of "show mobility summary" of all 4 controllers & ensure members are up. Also consider configuring a multicast group for mobility communication to optimize mobility communication.



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Community Member

Re: 4 WLCs client MAC flapping

Hello Rasika,

Thanks for the tips, I'll definetely consider them.


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