Wireless Access

I've opened a pre-emptive case during our scheduled upgrade & I've posted these same questions to TAC, but I figure I'd get input from the community to see if anyone's experienced any troubles with AP Image Preload, newer code, & older APs. 

We’re planning on going from AOS 6.4.3.6 to 6.4.4.12.  

A pair of 7220 masters in an Active/Backup config & 4 x 7240 locals with VRRP Redundancy, 2 pairs in active-active configurations.  APs split across all 4 controllers via VRRP LMS-IPs.  2960 APs of different types: 187 x AP-105s, 60 x AP-124s, 1402 x AP-125s,  400 x AP-135s, 631 x AP-225s, & 3 x AP-275s.

I've used AP Image Preload previously, worked great!  Saw a few APs with errors, but nothing major. 

I’ve got a few questions…

1.       Will AP Image Preload work on all of the APs models listed, or might it fail on some (namely thinking about older AP-105s & AP-125s, possibly even AP-124s – Read some Community post suggesting AP-125s may not have enough memory to support the new image)?

2.       What happens if an AP can’t preload the updated image?  Is there a specific error message I should expect to see?  Will it try again later?  If unable to pre-load the upgrade image, will the older AP fail (impacting user service) or will it continue operating normally?  In the later, would that simply mean that the AP would reboot once the controller reboots during its upgrade – in essence not minimizing AP downtime for those AP types? 

3.       What happens if an AP can successfully preload, but reboots or resets PRIOR to the controller upgrade?  I'm guessing it would boot into the new code, communicate w/ the master, realize it needs to downgrade & then downgrade itself - potentially creating more downtime.  I'm guessing, once it comes back on-line, it will check-in & be pre-loaded once again. 

Thanks,

1.  Don't try preload on the 125s, 124s or 105s.  They simply do not have enough memory to be successful 100% of the time.

2.  The AP should continue to function if preload fails.

3.  Not sure.

Long story short, with what you have going on (VRRP, LMS, etc), you should not bother with pre-load.  If you have a fast LAN between the APs and the controller should finish in a decent amount of time (run "show ap database-summary" on the master to keep score).  Not preloading because you have some APs that might not succeed also means that you would minimize your steps and limit the amount of possible outcomes.  Typically you want to be able to predict where your APs end up, so rebooting all of your controllers at once is typically the best bet...