We have a mixture of 3825 and 3715 APs . After upgrading to v10 software we updated the AP firmware as usual. Trouble is we can get all 1,037 APs up to v10 firmware, wait a few days, and about 4 APs will show up with v9 firmware. Wait another day and the number jumps to 7. The same 7. I can set for Controlled upgrade, upgrade these 7, ssh into the AP, see it has v10 software, reboot, log back in to verify v10 software. I can set the controller to "Always Upgrade APs to default image" which is v10. No matter what within a couple days an AP or 2 show up with old v9 firmware. APs I have ssh'd into and seen the v10 as well as having the controller list them as v10. This cycle of events has repeated 4 times in the last 10 days.
It is as if they are factory resetting themselves for some reason. Does anyone know what is wrong? Are they just bad APs that need to be RMA'd?
Awesome. I usually test 1450 if 1400 works ... and then 1475 if 1450 works ... and if 1475 fails ... just go with 1450. No need to cut it too fine. I have seen certain environments that needed the MTU to be set below 1000 though to work properly. Glad you tested for your specific environment from the controller's location to the AP's location or vice versa. After you've performed the Controlled Upgrade to those 7 APs ... please let us know if the firmware version "sticks" better or not.
If you used Windows, specifying a size of 1472 bytes for the ping payload actually results in a 1500 bytes IP packet, because the IP and ICMP headers not taken into account with the -l option. Thus the MTU does not seem to be a problem in this case.
If the IP and ICMP headers are excluded from the size option of any given ping program depends on the implementation.
Did you regressively ping test using the -f and -l parameters until you reached a threshold where the pings would go through without being fragemented?? Or did you just take the 1400 value given as an example in the KCS article and apply that without testing? Your network may require a lower MTU or may even allow a higher MTU ... than the example given in the article. Just trying to make sure you get the best result possible. There may be something else afoot here ... but getting the MTU set correctly can only improve controller <> AP communication and increase the chances that the upgrade goes smoothly and correctly.