Hi,
I didn't find any OIDs, I ended up writing and scheduling a script that takes the raw data from the registration table and FTPs it to my monitoring server where another script pushes the data in to the monitoring system. It works pretty well and gives me all the info I need.
:local filecontent;
/file remove [find name=reg-list.txt]
/file print file=reg-list.txt
/file set [find name=reg-list.txt] contents=""
delay 1s;
:foreach int in=[/caps-man registration-table find] do={
:set filecontent ($filecontent . [/caps-man registration-table get $int ssid] . "::" . [/caps-man registration-table get $int interface] . "\r\n");
}
/file set [find name=reg-list.txt] contents=$filecontent
:set filecontent ("")
delay 1s;
/tool fetch address=X.X.X.X port=21 src-path=reg-list.txt user=username mode=ftp password=password dst-path=reg-list.txt upload=yes
delay 5s;
/file remove [find name=reg-list.txt]
The output looks a bit like this (depending on how you identify your APs in the registration list, Mine all start with 'cap')...
ssid1::cap001-1
ssid1::cap001-1
ssid1::cap001-2
ssid2::cap001-1-1
ssid1::cap001-1
ssid2::cap002-2-1
ssid1::cap003-2
ssid1::cap001-2
ssid2::cap001-2-1
The output let's me count the total registrations (although there is an OID for that .1.3.6.1.4.1.14988.1.1.1.6.0) by counting the lines, count the clients per access point (by counting, e.g. cap001, cap002), the clients per said (by counting ssid1, ssid2 etc.) and clients per ssid on each radio, e.g. ssid1::cap001-2 is ssid1 on the 5GHz radio of cap001, etc. etc.