Yep, I was referring to the entries I see in my logs for "Interim-Update", which is of course an Accounting record, and I had always assumed this went with an Auth as well, but have never looked in detail to see! So I am most likely talking rubbish!
No, that's accounting, which is completely different to authentication. You don't normally return *anything* in accounting - just an "ok, message received" to stop the retransmit logic. The packet flow for a wireless client normally looks something like this: ap/controller: access-request radius server: access-challenge ...repeated a few times to complete EAP & EAP-inner ap/controller: access-request radius server: access-accept w/ VLANs This is the "authentication". You then get: ap/controller: accounting-request Acct-Status-Type=Start radius server: accounting-response # then every Acct-Interim-Interval ap/controller: accounting-request Acct-Status-Type=Interim-Update radius server: accounting-response # You might have 0, 1 or more repeats of the authentication phase here, depending on how your wireless re-auth settings are. This may or may not stop/re-start the accounting session # then when the client disconnects ap/controller: accounting-request Acct-Status-Type=Stop radius server: accounting-response