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

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