[TriLUG] sourcing outbound traffic from internal NIC

[Clay Stuckey]

I found part of the solution. Ip route default via [gw ip] src [int  
ip]. I have to remove the default gw first. This handles the issue at  
layer 3. My only issue is now to find the right way to make it persist  
a network restart. At the moment, I have a cron job that checks for a  
gw and will execute the ip route command if needed.

--
Clay Stuckey
(919) 600-0486
claystuckey at gmail.com

On Dec 6, 2009, at 2:27 PM, Aaron Joyner <aaron at joyner.ws> wrote:

> 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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