Thanks for that edit earlier This time it's serving a session timeout of 0 As an update, we are aiming for getting the actual Session-Timeout value from the reply or the difference in seconds between now() and the WISPr-Session-Terminate-Time - Whichever value is smaller Here is the new output Any tips would be much appreciated! /// Login OK: [22-22-22-22-22-11/password] (from client wificpa port 0) # Executing section post-auth from file /etc/freeradius/sites-enabled/wifirush.rad +- entering group post-auth {...} ++? if (reply:WISPr-Session-Terminate-Time) ? Evaluating (reply:WISPr-Session-Terminate-Time) -> TRUE ++? if (reply:WISPr-Session-Terminate-Time) -> TRUE ++- entering if (reply:WISPr-Session-Terminate-Time) {...} expand: %{reply:WISPr-Session-Terminate-Time} - %l -> 2000-11-01T12:22:23+00:00 - 1541009986 Not a number at "T12:22:23+00:00 - 1541009986" expand: %{expr:%{reply:WISPr-Session-Terminate-Time} - %l} -> +++[reply] returns noop ++- if (reply:WISPr-Session-Terminate-Time) returns noop Sending Access-Accept of id 247 to 96.227.97.217 port 57890 WISPr-Bandwidth-Max-Up = 5000000 WISPr-Bandwidth-Max-Down = 5000000 Mikrotik-Rate-Limit = "" Acct-Interim-Interval = 300 Session-Timeout = 0 Idle-Timeout = 900 WISPr-Session-Terminate-Time = "2000-11-01T12:22:23+00:00" Finished request 1. Going to the next request Waking up in 0.5 seconds. Cleaning up request 0 ID 246 with timestamp +4 Waking up in 4.4 seconds. Cleaning up request 1 ID 247 with timestamp +9 Ready to process requests. ////