The current long term 17.12 release of the IOS-XE 9800 WLC is feature packed, but tucked away in the release notes is a one liner that is sure to catch people out in the near future(or me the other day):
From this release, the default console baud rate of the 802.11AX APs is changed from 9600 bps to 115200 bps.
What does this mean?
Well, digging a bit deeper, it only covers the Cat9k range of AP’s, so 9120, 9130,9136, 916x, etc
AND
It only impacts new (or factory reset) AP’s when they join the controller running 17.12 or higher. So if AP’s are already joined to the controller and are upgraded from 17.9.x to 17.12.x then they will still use the old 9600bps rate, but then if you add a new AP to the controller, that will use the new setting of 115200bps.
If an upgraded AP is set back to factory default though and joins the controller again, it will assume the new 115200bps config. So you could/will end up with some AP’s on the old 9600bps config and some on the new 115200bps config. Or, once upgraded to 17.12 or higher then factory reset all AP’s from the CLI/GUI (not recomended unless you are bored and have a lot of time and a real reason to do this), and then you’ll have a standard across the board, no matter which AP you connect to (that’s a Cat9k AP anyway, Wave1/2 are not impacted by this!).
WHY?
Turns out the reasoning for this is simple, it’s so that the AP can boot faster!