Force traffic out the same interface it came in on

[dave.kilpatrick]

My post is regarding winodws 2003 but I wanted to post it here as well
becuase there isn't a networking group for windows 2003.

I have a windows 2003 standard edition server with ISA server 2004 SP2
installed. It has two NICs (10.0.1.18 and 10.0.1.19), I want the
traffic to go out the same interface it came in on. I have tried to
use static route using the route add command, but the default route
windows puts in is forcing traffic coming on 10.0.1.19 to go to
127.0.0.1 which in turns send it to 10.0.1.18. Is there a way I can
move my static routes (send data from 10.0.1.19 to 10.0.1.19) above the
default routes?

Or another solution?

Thanks

 

[Phillip Windell]

My post is regarding winodws 2003 but I wanted to post it here as well
becuase there isn't a networking group for windows 2003.

I have a windows 2003 standard edition server with ISA server 2004 SP2
installed. It has two NICs (10.0.1.18 and 10.0.1.19), I want the
traffic to go out the same interface it came in on. I have tried to
use static route using the route add command, but the default route
windows puts in is forcing traffic coming on 10.0.1.19 to go to
127.0.0.1 which in turns send it to 10.0.1.18. Is there a way I can
move my static routes (send data from 10.0.1.19 to 10.0.1.19) above the
default routes?

No. It will use the Primary IP# (which is *.18). The *.19 is a secondary
IP#. Your root problem is that your expectations are incorrect and you
should never even want it to matter that is uses *.18 as the source for the
outbound packets and you should not create a situation where that would ever
matter.

Also keep in mind that with TCP/IP the inbound and the outbound are two
entirely different things that have no relationship or bering on each other.
They are totally independent of each other. The outbound decision has no
idea what IP something came "in" on because there is just simply no
relationship between the two. Routing decisions are always initially made at
the "source",...so the inbound decicion had nothing to do with this machine.
The outbound however has the decisions made at this machine and it is only
"known" routes that can choose a particular Source (interface) for the
outbound packets,...however the "unknown" routes will always use the Default
Gateway (0.0.0.0 in the Table) which is always going to be associated with
the Primary IP# of the nic from the subnet that matches the subnet of the
Default Gateway.

 

[Kurt]

The default route is at the top of the route list and is the last thing to
execute. It is also refered to as the "route of last resort". The route
table (in windows) is executed from the bottom up. Any static route will
override the default route.

....kurt