I have a customer who has 1 x WLAN 4402 Controller. Everything is working perfectly until last week when we add another 4402 to act as HA.
After that, i can no longer ping the management IP of the 1st WLAN controller, nor getting into the web mgmt interface. However, everything on the 2nd new controller works perfectly.
Mgmt IP of 1st 4400: 10.120.16.2
Mgmt IP of 2nd 4400: 10.120.16.4
I have spent a lot of time on this but still couldn't figured out why.
More info on the attached files.