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

[jalba]

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.

[Andrew Shoop]

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.