Enable 802.1x and RADIUS on the Adminster/Diagnostics page, and track a client MAC connecting to a DVLAN enabled WLAN.
I cannot find the exact date for ZoneDirector, but I can confirm SmartZone has had rfc-5176 compliance since 2.5.1 release.
Last I could find, SZ 3.2.1 patch for Framed-IP attributes value received not used for session validation or Acct-Terminating-cause
is not sent back in 'accounting stop'.
If you need assistance with troubleshooting, Tech Support would be able to assist.