Switch Reporting Ports are Flapping Constantly

[pbiggs]

We have a switch dedicated to our Wireless Access Points. We are getting repeated flapping of port notifications in our SEM. Any idea why this would be happening and how to resolve the issue? 

Here is the output from one of the events but there are many more.

Jan 26 14:01:27.242: %SW_MATM-4-MACFLAP_NOTIF: Host 2adc.bdfb.0fde in vlan 201 is flapping between port Gi1/0/2 and port Gi1/0/10

Thank you for your help. 

[liviu.gheorghe · Accepted solution]

Hello @pbiggs ,

the message indicated that a certain MAC address, 2adc.bdfb.0fde, that was known on a port, Gi1/0/2, now is "seen" on a different port - Gi1/0/10.

This happens in a redundant layer 2 topology when there is topology change and the Spanning Tree Protocol reconverges, or in the case the layer 2 topology has a loop causing MAC addresses to "flap" between different switch ports.

Depending on the number and frequency of the flap messages, it could indicate a problem with the layer 2 topology - a loop for example, or could be normal operational messages if number of messages are low. 

The message could indicate a problem of configuration with STP.

[pbiggs]

Thank you for this information. I will look into this. Its a Cisco 9300L 48 port switch that is dedicated to our WAPs. Someone had advised to enable portfast on the ports the Access point are connected to. I'm trying it on two of the ports first to see if the events stop at least on those ports before trying this on the other ports. Also, they indicated BPDU filter may cause an issue but we do have this enabled on the switch. I will update as further information becomes available. 

[Georg Pauwen]

Hello,

on a side note, the MAC address belongs to an Apple device...

[pbiggs]

Yes, I did notice this as well. Most probably an IPhone. 

[MHM Cisco World]

no mac address-table notification mac-move

If you sure this mac for wifi client 

This mac flapping is for wifi client when l2 roaming disable these notifications 

MHM

[pbiggs]

These should be all Wi-Fi clients but as you said I need to confirm that first. Thank you very much for this information. I sure it will be very helpful. 

[pbiggs]

So far I have added spanning-tree portfast trunk to the WAP interfaces of the switch and I am no longer receiving these messages regarding ports flapping so I believe this has been resolved. Thank you all for helping me out with this issue. 

[MHM Cisco World]

Wait for few days and monitor SW log.

Update me when you face same issue 

MHM

[pbiggs]

Thank you for following up with me. I'm guessing from your response you believe this will not fix the issue? I'm hopeful but if it does happen again I will update it here. I also have your recommendation which I will try as well. I found that solution under another users entry here and they said it had worked for them and since doing the same I have not had the messages pop back up. If I do I will reach back out. Once again thank you for your help with this.