hi thisisnotaswan
there is no mib OID for that stat, but that stat is also not the current number of dot1x sessions on the controller. For this, you should consider the OID wlsxNumOfUsers8021x in the aruba-user.my MIB.
I have seen some customers plot the whole group as stacked values if using multiple services on the controller, can make for a nice plot.
[root@mibs]$ snmpwalk -v2c -c public -M. -mALL 10.1.1.1 wlsxUserStatsGroup
WLSX-USER-MIB::wlsxNumOfUsers8021x.0 = Gauge32: 18
WLSX-USER-MIB::wlsxNumOfUsersVPN.0 = Gauge32: 7
WLSX-USER-MIB::wlsxNumOfUsersCP.0 = Gauge32: 0
WLSX-USER-MIB::wlsxNumOfUsersMAC.0 = Gauge32: 0
WLSX-USER-MIB::wlsxNumOfUsersStateful8021x.0 = Gauge32: 0
There is a caveat for this stat. If ipv6 is enabled and the client is dual stack - or the client is leaking multiple IP addresses (i.e. has vm installed), then the number of dot1x users in the user table can be larger than the number of associated clients. In fact, for the above output, there are just 9 stations associated, all are dualstack and consuming 1 x ipv4 + 1 x ipv6, hence 18 dot1x 'users'.
WLSX-WLAN-MIB::wlanESSIDNumStations[STRING: dot1xnetwork] = Gauge32: 9
WLSX-WLAN-MIB::wlanESSIDEncryptionType[STRING: dot1xnetwork] = BITS: 02 00 wpa2-8021x-aes(6)
In summary, depending on whether you really want to know the number of users in the usertable, including any dualstack clients, then you can use wlsxNumOfUsers8021x OID. or, if you just want to track actual associated clients irrespective of the IPs being used, then use the wlsxWlanESSIDTable and sum together the rows that correspond to dot1x.
regards
-jeff