From owner-freebsd-questions@FreeBSD.ORG  Wed Mar 14 19:22:48 2007
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Subject: Re: per-interface default routes?
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On Wed, 14 Mar 2007, Mark Messier wrote:

> Suppose you have a freebsd box with two LAN interfaces,
> one numbered on netA and one on netB...
>
> Some applications are listening on the netA IP address, some on the
> netB IP address.  Some applications may be listening on all interfaces
> but might have a directive that indicates which IP address to use for
> packets sourced from the application, like this:
>
> 	query-source address 192.0.2.2 port 53;
>
> What I want to happen is that packets sourced from the
> netA IP address go out the netA physical interface
> and packets sourced from the
> netB IP address go out the netB physical interface.
>
> That is, I want per-interface default routes
> (is this the correct term?).
>
> How do I do this?
>
> Thanks,
> -mark

Route has more information if you want to setup default routes for interfaces. Either that, or natd will yield a solution for you.

-Garrett