Freeradius as DHCP sending DHCP Offer to interface where default gateway is

[Urazaev Vadim]

Hi All.
I`m trying to set up freeradius as dhcp server and everythins seem to be 
ok, in radiusd -X I can see the DHCP-Discover packets that comes from 
client and DHCP-Offer that server sending to client.
When I tried to find out to which interface server send`s responses I 
saw that responses server put into interface where dafult gateway is
In configuration of dhcp listener there is an option "interface", but 
when I tried to set it up I see a message
Failed binding to interface "ifname": "bind to device" is unsupported

My question is: Is there solution for this situation ?
Freeradius ver. 2.1.10 from git
OS: FreeBSD 7.2-RELEASE-p8