[olug] iptables behind router

William E. Kempf wekempf at cox.net
Mon Sep 13 17:08:08 UTC 2004


Here's my network topology:

[cable modem (cox)]<--->[router]<--->[comp A]
                                <--->[comp B]
                                <--->[WAP]<--->[laptop]

The router is a Linksys router, and the built in firewall is minimalistic
(well, at least what's readily available with out hacking... I realize
it's a Linux box under the covers).  For me, the biggest problem is that
it only allows you to forward 5 ports, and I run a lot more servers than
that.  So, I DMZed [comp A], my Linux box, and have set up iptables on it.
 I can open specific ports on this computer easily enough, so for the most
part life is grand.  However... I'd like to be able to have [comp A]
forward some ports to [comp B].  (I realize I'm not using all of the
proper terminology here... I'm just learning about networking at this
level.)  IOW, [comp A] will handle all of the routing from external to
internal.

All of the documentation I've read assumes that [comp A] will have
multiple interfaces, and it does not.  Is it possible to do this, and if
so, what are the rules I need to get it to work?

-- 
William E. Kempf
wekempf at cox.net



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