Capture the MAC address of VPN connecting devices in FreeRadius

[NiTr0]

> In the Calling-Station-Id i get the device IP Address and not the MAC!

How  you  want  to  retrieve  a MAC if VPN client can be theoretically
behind  one  or more routers and, at all, it can use non-Ethernet link
to  accessto  the  VPN  server?

If you want to get MAC - use PPPoE for clients, or make MAC fixation
by scripts, or use something like ipguard...