NAT with one NIC?

NAT with one NIC?

Post by Mike Newma » Fri, 01 Feb 2002 17:08:19



Is it possible to do NAT with only one NIC in my Redhat Linux 7.2 box?

--
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NAT with one NIC?

Post by Tauno Voipi » Fri, 01 Feb 2002 17:37:01



Quote:> Is it possible to do NAT with only one NIC in my Redhat Linux 7.2 box?

Yes - it is, but definitively *not recommended* due to the security
problems.

The trick is to assign two IP addresses to the interface: one for the
external network and another for the internal network.

However, you need to connect the external network box (ADSL, cable,
whatever) to the same hub as the internal network. This provides no physical
separation of the networks, and your internal network is quite visible to
the outside.

The visibility can be a problem - I have an ADSL connection 24h/day. There
are some 20 - 40 unallowed connection attempts per day and about once per
week a complete aggressive port-scan on the firewall. If the internal
network is visible to the outside, you need to provide the protection to all
computers separately. This usually is much more expensive than the second
NIC in the firewall/router.

And - do not say that a home user does not need protection. This is the
attitude that turns the home users to spreaders of the infections.

Tauno Voipio


 
 
 

NAT with one NIC?

Post by James Knot » Fri, 01 Feb 2002 22:35:40



> Is it possible to do NAT with only one NIC in my Redhat Linux 7.2 box?

Yes.  Just set up an alias for the 2nd IP.  However, if you're building
a firewall, 2 NICs are strongly recommended.

--


james.knott.

 
 
 

NAT with one NIC?

Post by irado furioso com tud » Sat, 02 Feb 2002 00:11:05


my own experience says a big *no*, it is *not* possible, while I tried
very hard with slackware and SuSE. Anyone with *positive* experiences on
this??

the (my) original, logical topology was a link-->/linux gw+fwall/-->lan.
The phisical topology was linkz-->switch/---><--/linux../
[                                      |
[                                      |---> lan


>>Is it possible to do NAT with only one NIC in my Redhat Linux 7.2 box?

> Yes.  Just set up an alias for the 2nd IP.  However, if you're building
> a firewall, 2 NICs are strongly recommended.

--

sauda??es,

Irado Furioso com Tudo
Linux (SuSE) User 179402
tortura sempre instrumento do estado, dos pais, dos professores..
sempre algum se imagina ter poder acima dos demais. Viva a anarquia!!!

 
 
 

NAT with one NIC?

Post by D. Stuss » Sat, 02 Feb 2002 10:31:17



>Is it possible to do NAT with only one NIC in my Redhat Linux 7.2 box?

Of course.  However, to be useful, a second network connection of some sort
should be present (e.g. PPP, SLIP, PLIP, etc.), especially for masquerading.