Making sense of Cisco WLC access point firmware pre-download
Firmware pre-download on the Cisco WLC wireless LAN controllers is a beautiful thing.
“In the old days"™ the update went like this:
- Upload firmware to controller
- Reboot controller
- Accesspoints want to rejoin controller, see non matching firmware, start updating, 10 at a time … 1 hour later …
- Most of your APs updated, some are still updating…
In large wireless LANs, this was not really an ideal solution, as the Wi-Fi was down for a long time if you had many APs on the controller. So Cisco introduced the pre-download feature with version 6.0, many years ago. It is documented in the official config guides, for example here.
The issue I have with this, that it was not really clear to me, which primary/backup command does what, because you have primary and backup images on WLC and AP.
So here a little guide, with the example of a usual upgrade path: