topic mac-flapping between both controllers (AIR-CT5508-K9) in Wireless

mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Mon, 05 Jul 2021 15:45:01 GMT

Hello, we have two WLC in different places and we see that we have mac-flapping between both sites.

In each site we have a port-channel in mode on, and the load-balancing method is src-dst-ip.

What could be the cause?

Site A: Primary WLC

Jun 19 12:28:33.069: %MAC_MOVE-SW1_SP-4-NOTIF: Host xxxxx in vlan xx is flapping between port Po15 and port Po71

Site B: Secondary WLC

Jun 19 12:28:25.679: %MAC_MOVE-4-NOTIF: Host xxxxx in vlan xx is flapping between port Po71 and port Po25

Po71 is the Po that connects with the WLC in each side, and Po15 and Po25 are the interconnections between both sites.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

Scott Fella — Tue, 19 Jun 2018 13:44:09 GMT

Are devices moving from one building to another or roaming from one AP one one WLC to another AP on the other controller? Or are the WLC just in different locations in the same building. If so, that’s why you are seeing these.

You can search the forum and others have posted questions and answers to the map-flapping like what you see.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Tue, 19 Jun 2018 13:58:42 GMT

The WLC are in different places, its not possible to have roaming between them,

WLC are configured with SSO redundancy.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

Scott Fella — Tue, 19 Jun 2018 14:49:09 GMT

So you have two WLCs in SSO but are in different physical locations in different buildings? You should not see Mac flap unless there was a switchover.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Tue, 19 Jun 2018 14:55:56 GMT

Yes, are in different locations and in different buildings, i dont see where its the problem, there is not any loop and only wlc1 its working like primary wlc. Why we see the mac flapping continuosly? in the events of the WLC we dont see any switchover.

Its seems like any client that connects into the network you can see the mac in wlc1 and in wlc2 during some time, if not i dont understand this situation.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

Scott Fella — Tue, 19 Jun 2018 14:59:09 GMT

Open a TAC case and see what they say. I’m assuming that it’s non-impacting and it’s just annoying seeing the logs.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Tue, 19 Jun 2018 15:46:57 GMT

Yes, I suppose that i need to open a case, the only problem is that we dont have log, because all the day this messages are fill all the log buffer.

Regards

Re: mac-flapping between both controllers (AIR-CT5508-K9)

Scott Fella — Tue, 19 Jun 2018 16:48:09 GMT

TAC would want to look at the messages and the verify the configuration and code.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

techtommy — Tue, 19 Jun 2018 19:05:13 GMT

Are any of the AP`s in flexconnect mode? I recently saw that same experience with a customer that was running Flexconnect. As the client roamed from one IDF to another, it generated mac flap notifications.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Wed, 20 Jun 2018 08:18:20 GMT

Only a few APs are in flexconnect mode, but the macs are not in these APs, so the problem happens to all the APs, not the flexconnect only.

Regards

Re: mac-flapping between both controllers (AIR-CT5508-K9)

patoberli — Wed, 20 Jun 2018 09:27:05 GMT

Probably a stupid question, but are you sure they are actually running in SSO and not in standalone mode?

Re: mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Wed, 20 Jun 2018 09:34:17 GMT

Yes, if you see in the redundancy tap, you can see "SSO" in redundancy state

Re: mac-flapping between both controllers (AIR-CT5508-K9)

patoberli — Wed, 20 Jun 2018 09:36:26 GMT

Ok good. I had this "issue" with those messages too, but with two standalone WLCs. Do you maybe have two different SSIDs setup where the same user can connect to, but is getting a different IP address?
That could cause this, if the client roams from one to another SSID.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

jalba — Wed, 20 Jun 2018 10:27:25 GMT

The normal situation is that one WLC is managing everything, so its not normal that you see these macs in the secondary WLC.

Because all the APs, SSIDs are in the primary WLC.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

patoberli — Wed, 20 Jun 2018 11:10:03 GMT

It can happen, if you have two SSIDs with different IP ranges and a client hopping between the SSIDs. In those cases, the client will get a new IP address and the load balancing on the Layer2/3 might route him through another interface, but with the same MAC address.

Re: mac-flapping between both controllers (AIR-CT5508-K9)

Andrew Shoop — Fri, 22 Jun 2018 18:30:56 GMT

Just a note, since you mentioned some APs are FlexConnect ...

FlexConnect APs, when combined with a FlexConnect enabled SSID, deliver a host's traffic directly onto the local switch port the AP is connected to.

In your example, this traffic would be seen in the central location as coming from your sites (Po25). However, if another AP in the same location was not in FlexConnect mode, that traffic would tunnel to the WLC, and in this case be seen as coming over the WLC's port (Po71).

Therefore, from the perspective of the switch in the central location, the MAC would appear to transition from Po25 to Po71.