Well, that's the problem. We have never cleared the config on these old APs, and they are using ap-groups that are still in existence and have not been changed since these APs were provisioned. So they were up, went down, and then eventually just vanished from the lists. I've never done any housekeeping, though there was a software upgrade during that time.
I understand that we don't contact the APs directly, we're trying to poll the controllers using SNMP.
The issue for us is that we need to be able to know that the information we receive on our down APs is accurate. Without knowing why some of these APs are not being listed, then we cannot know with confidence that the information being provided either by SNMP or the GUI is accurate.
From that link: "By default, any AP that has booted to a controller creates an entry on that controller and the master controller's database, forever. If that AP is no longer in your system, it still shows up in the AP Down number on the master and local controller"
This is not what has happened. Those APs are no longer showing up in the AP Down numbers...