natd -redirect_port

[Anthony Philipp]

hello,
im am trying to redirect various ports through my gateway, a freebsd machine, to other machines. when i type:
natd -interface rl0 -redirect_port tcp 10.10.10.4:25 25
to redirect port 25 to 10.10.10.4 on port 25 it tells me
natd: Unable to create divert socket.: Protocol not supported
rl0 is the external ethernet card. if i dont use -interface, it says that the aliasing address is not given. any help is appreciated. am i running freebsd 5.2-release
anthony