Linux NAT questions

Linux NAT questions

[Sim, CT (Chee Tong)]

what I am trying to do is this. I have a genuine network, say 1.1.1.x, and
my Linux host is on it, as 1.1.1.252 (eth0). I also have a second network at
the back of the Linux box, 192.168.200.x, and a web server on that network,
192.168.200.2. The Linux address is 192.168.200.1 on eth1. 

What I want to do is make the web server appear on the 1.1.1.x network as
1.1.1.160. I have done this before with Firewall-1 on NT, by putting an arp
entry for 1.1.1.160 to point to the Linux machine eth0. The packets get
redirected into the Linux machine, then translated, and then routed out of
eth1. 

The benefit is that there is no routing change to the 1.1.1.x network, and
the Linux box isn't even seen as a router. 

I would appreciate any help with this. Any command to do this?  

Chee Tong


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RE: Linux NAT questions

[Michel Wilson]

> what I am trying to do is this. I have a genuine network, say 1.1.1.x, and
> my Linux host is on it, as 1.1.1.252 (eth0). I also have a second
> network at
> the back of the Linux box, 192.168.200.x, and a web server on
> that network,
> 192.168.200.2. The Linux address is 192.168.200.1 on eth1.
>
> What I want to do is make the web server appear on the 1.1.1.x network as
> 1.1.1.160. I have done this before with Firewall-1 on NT, by
> putting an arp
> entry for 1.1.1.160 to point to the Linux machine eth0. The packets get
> redirected into the Linux machine, then translated, and then routed out of
> eth1.
>
> The benefit is that there is no routing change to the 1.1.1.x network, and
> the Linux box isn't even seen as a router.
>
> I would appreciate any help with this. Any command to do this?
>
> Chee Tong
This isn't really a kernel question. I think you'd better ask it on some
linux network list/newsgroup. But here's an answer anyway....

You could add 1.1.1.160 to eth0:
   ip addr add 1.1.1.160 dev eth0
and then use NAT to redirect these to the webserver:
   iptables -t nat -A PREROUTING -p tcp --dst 1.1.1.160 -i eth1 -j
DNAT --to-destination 192.168.200.2

This should work, AFAIK, but i didn't try it myself. You could also try to
use the arp command (see 'man arp'), but i don't know exactly how that
works.

Good luck!

Michel Wilson.