iptables firewall between dsl router and intranet

From: Thomas Olschewski (junk_at_innomic.de)
Date: 07/27/05 

Date: Wed, 27 Jul 2005 08:31:54 +0200

Hello,

I had setup a iptables based linux firewall. It was connected with eth0 to
the internal network and with eth1 to a dsl modem (pppoe) and did also all
the NAT stuff. A lightning strike blows my modem and the new dsl hardware is
a router itself, providing NAT, voip etc. Nevertheless I would like to use
my iptables firewall between this router and my internal network.

Internal network is 192.168.5.x

Questions
Is it a good idea to set the unsecure nic eth1 of the firewall and the dsl
router to another net, for instance 192.168.6.x?
How are the machines of the internal network routed? Is the gateway ip the
ip of the firewall's secure nic eth0? I suppose it is, but how is the
firewall networking setup? Does it need also a gateway ip, the ip of the dsl
router? Can this be the default route or do I have to setup different routes
for eth0 and eth1?

I hope someone can enlighten me.

Thomas

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