Symptom
An AIR-CT5520-K9 or AIR-CT8540-K9 may fail to boot, showing console errors similar to the following:
Configuring network interfaces... done.
*********************************************************************************
******* *******
******* FATAL ERROR!!!!!! *******
******* This hardware is either Cisco 8540 or 5520 Wireless LAN *******
******* Controller. System could not find 68xx Nic Card. System *******
******* will reboot in 10 minutes!!! *******
Conditions
Seen with new, out of the box 5520s and 8540s.
May also be seen when an operational WLC is rebooted.
Workaround
1. Upgrade to CIMC 3.0.3f or above. The upgraded CIMC will detect the presence of the Cavium card, and will set the fan policy to "Balanced", which will enable the box to boot.
2. If using earlier CIMC, manually change the fan policy from "Low Power" to "Balanced".
3. If you can get AireOS to boot, upgrade to one of the following AireOS releases, which will ensure that the fans are running at adequate speed at boot time:
8.2MR7 (interim available from TAC; to be released on CCO in CY18)
8.3MR3esc (8.3.130.5 or above, available from TAC)
8.3MR4 (interim available from https://supportforums.cisco.com/t5/other-wireless-mobility-subjects/8-3mr4-interim-availability/m-p/3307086; to be released on CCO in Q1CY18)
8.5.110.0 (and above)
8.6 (and above)
Further Problem Description
This problem was due to the fans not running fast enough at boot time.