I spent a few days on this weird issue when trying to convert and configure 3800 AP for Mobility Express (ME) and assign working IP address. I started by connecting AP to regular user Vlan, booted up, from AP prompt updated code to ME version. Rebooted, went through setup and assigned static IP on user Vlan. After last reboot I webbed into WLC and all looked good, internal AP registered and all Radios were up. Now it was time to move it to dedicated management Vlan. Through console, I changed WLC IP and changed Vlan on the switch port. After AP was reconnected and came back up I could not communicate to WLC IP any longer. On switch port, I saw only AP MAC address.
At the same time, I was getting these error messages.
[*11/07/2018 20:02:09.8664] Waiting for uplink IPv4 configuration
[*11/07/2018 20:02:14.8676] Waiting for uplink IPv4 configuration
[11/07/2018 19:56:21.0900] wired0 emac 0: link up
[11/07/2018 19:56:21.1400] wired0: link up
[11/07/2018 19:56:21.1900] wired0: started
[11/07/2018 19:56:36.3800] wired0: stopped
[11/07/2018 19:56:37.0600] wired0 emac 0: link up
[11/07/2018 19:56:37.1200] wired0: link up
[11/07/2018 19:56:37.1600] wired0: started
Something clearly was preventing communication between the switch and AP.
After several troubleshooting hours, it became clear that WLC IP connectivity is heavily depending on AP IP address presence. My management Vlan did not have DHCP enabled so AP never got assigned IP address. This somehow prevents any WLC communication with the network. After I’ve enabled DHCP on management Vlan and rebooted AP connectivity restored to normal.
Most likely you will be trunking AP port on the switch so make sure native Vlan is set up as your management Vlan with DHCP enabled.