1) All 24 access points are in the same AP Group and have identical configuration.
2) All 24 access points are on the same subnet and have the same default gateway
The only difference is the physical connection (15 AP on one switch, 9 ap on another switch).
I run "show ap database long" on the backup controller (which is the master controller). Nine access points that are switched to backup controller are showing "D" flag.
Below is the result for two APs (one is switched and one is not)
AP Database
-----------
Name Group AP Type IP Address Status Flags Switch IP Standby IP Wired MAC Address Serial # Port FQLN Outer IP User
---- ----- ------- ---------- ------ ----- --------- ---------- ----------------- -------- ---- ---- -------- ----
...
6c:f3:7f:ca:30:b0 Group1 105 AP-IP-Address1 Up 9h:31m:11s D BACKUP-LMS-IP-ADDRESS 0.0.0.0 6c:f3:7f:ca:30:b0 BT0251796 N/A N/A N/A
6c:f3:7f:ca:30:b5 Group1 105 AP-IP-Address2 Up 11h:35m:27s LMS-IP-ADDRESS 0.0.0.0 6c:f3:7f:ca:30:b5 BT0251801 N/A N/A
....
Also, you can note that uptime for the AP which is switched is less, because we were rebooting it, trying to fix the issue.
I would imagine that 9 APs that are not working are not seeing the LMS correctly, but I can ping LMS from their switch no problem. Unfortunately, I do not see any troubleshooting opportunities "fom inside "the AP itself.