The control path between our Guest Anchor WLC4402 and one of our foreign controllers is down all other control paths are up as are all of the data paths. The Anchor is behind a firewall the configuration of which must be ok due to the other WLCs data and control paths being up. Can anyone tell me how I check that the WLCs are reciving each others mobility packets e.g. via debug.
debug mobility keepalive
you should see a "data path" keepalive every 10 seconds and a "control path" keepalive every 30 seconds.
I believe the Control Path will be a message about port 16666.
Run this from all controllers and verify who is sending the keepalive (I believe it is lowest mac address).
Bottom line is that if you see one controller send it, and the other doesn't recieve it, that sounds like it is getting lost along the way.
I've seen configuration before where if the DMZ Controller is the initiator of the keepalive (high mac address?), then the path may be down. It had to do with the firewall allowing the session from Trust to DMZ (and the return traffic), but not allowing the DMZ to initiate the session.
You could try an mping from both controllers and see if you can get a response....?