Does AP need to follow Cisco WLC upgrade path – a small test

Does AP need to follow WLC upgrade and get the intermediate release? Or will the Access Points survive if it skips the intermediate release?

The release notes says yes – “When you upgrade Cisco WLC to an intermediate release, wait until all the APs that are associated with Cisco WLC are upgraded to the intermediate release before you install the latest Cisco WLC software. In large networks, it can take some time to download the software on each AP“.

They don’t specifically say why, so I wanted to test for myself for several reasons
1) I’m curious about the outcome
2) Upgrading large networks can take a lot of time – could this be a possible short cut to use (if the benefits of the gambling on an unsupported path outweighs the actual danger of going an unsupported path)
3) What happens if there is an AP not online at the time of upgrade? Will it be stuck?

If one took a such a short cut – one could hope that a rollback to previous release is all you need in a worst-case scenario.

Thoughts
One could also do a test by removing connnectivity between all APs and WLC prior to the upgrade. Then upgrade the WLC to the desired software level and then reconnect just a few different APs/models to see what happens. If they are successful, one could open up for all APs. If not – downgrade.

My little simple test:
I cut off one of the access points (cap2702), upgraded a WLC 5508 from 8.2.100.0 > 8.3.143 > 8.5.140 – waited for the network and the rest of the APs to stabilize and then connected the cap2702 back on the network.

It worked. The AP joined the WLC and upgraded itself to v8.5.140.
This does not mean it will work for all releases and all models, but it is good to know that stranded APs at least have a chance of finding the WLC and getting upgraded.
A safer bet is of course to predownload the intermediate release during normal operations, so the total service interruptions won’t be that massive.

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