Migrating existing captive portal

Hi there,
I’ve searched the forum to try a solution for my problem, but had no luck.

Users in our corporate LAN are required to login to an Hotspot to access the net. The hotspot is a custom made solution (well) written in php and using the IPFW/IPTRAF firewalls to enable/check/disable the single user network access (in the prerouting chain). I’d like to move to a NAC solution based on mikrotik, so I spent some time experimenting with RB5009, using HotSpot and RADIUS client on a ethernet interface. Authentication data are stored on a freeradius server, which is bounded to an AD domain. I can reach the RADIUS server, but the only log line I see is:
Auth: (7255) Login incorrect (No Auth-Type found: rejecting the user via Post-Auth-Type = Reject):

As far as I can understand, the client is not talking “eap” to the server, so authentication fails. Reading the forum I see that there is no NAC solution “out of the box” but I wonder if someone has a workaround for this. Otherwise I’ll install the original corporate “captive portal” in a debian box using the container feature, even if I think it’ll be a throughput-killer solution.

Thank you in advance for help/chatting/free-hugs.
Best regards.