[TriLUG] sourcing outbound traffic from internal NIC

[Aaron Joyner]

What IP traffic is sourced from can be determined by the application
(based on what IP it binds to, or what IP it received traffic on), so
you can't necessarily do this at the OS layer.  You can't do it w/ a
route, as that will only control where the traffic is routed (ie. what
interfaces it traverses, and ultimately where it leaves the box), not
what the source IP of the traffic is in the IP header.  You can make
it appear to remote hosts like all traffic has come from that IP, sort
of, by SNAT'ing traffic from the "internal" IP, but that may not be
what you actually want.  Can you provide some more details about what
original goal led you down this technical path?  If so, someone can
likely provide a good suggestion to accomplish what you're after.

Aaron S. Joyner


On Sun, Dec 6, 2009 at 11:02 AM, Clay Stuckey <claystuckey at gmail.com> wrote:
> I have a machine with 2 NICs. One is internet facing, the other internal.
> Anyone know of a way to have all internet-bound traffic sourced from the
> internal NIC's IP? I am thinking entering a default route rule that will
> specify to use the internal NIC. Has anyone tried this before?
>
> Clay
>
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