howto isolate 2 nics?

[Tod Merley]

On 9/22/06, Gene Heskett <gene.heskett at verizon.net> wrote:
> Greetings;
>
> We have a machine that has two nics in it, one with an outside, world
> visible internet address, and one with an address in the 192.168.xx.xx
> range.
>
> What we seem to be missing is a way to have requests for service generate
> the reply on the same nic it came in on, as its currently settup with just
> one gateway address, the replies are all going back out on the local
> address.
>
> We effectively need each nic to operate in its own domain, but with the
> machine servers visible to both nics?
>
> Can this be done?  URL's to tutorials?
>
> Thanks in advance.
>
> --
> Cheers, Gene
> "There are four boxes to be used in defense of liberty:
>  soap, ballot, jury, and ammo. Please use in that order."
> -Ed Howdershelt (Author)
> Yahoo.com and AOL/TW attorneys please note, additions to the above
> message by Gene Heskett are:
> Copyright 2006 by Maurice Eugene Heskett, all rights reserved.
>
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Hi Gene Heskett!

Sounds like the machine is a server?  Web, mail, that sort of thing?
As well, it is the supplier of internet to a local LAN (subnet
192.168.X.X).

You probably want Network Address Translation (NAT).  But yes, a basic
understanding of Networking is beyond a single e-mail typed by me at
4:36 a.m.

# The first two under "4.4.1. General" are probably a good place to
start, you should also see "Masquerading-Simple-HOWTO" (uses NAT).
http://tldp.org/HOWTO/HOWTO-INDEX/networking.html

# Shows most of the networking commands
http://yolinux.com/TUTORIALS/LinuxTutorialNetworking.html

# On the page do a search for "The Linux Network Administrator's
Guide" - 505 pages in the PDF version - very comprehensive.
http://tldp.org/guides.html

Two topics stick in my mind as I think about what you are trying to
do. One is security - you will need to understand how to manage a
firewall.  The second is a possible need to set up a Dynamic Host
Control Protocol server for those on the local subnet.

Have Fun!

Tod