[PLUG] iptables and NAT

["Ziegler, Scott" <scott_ziegler@merck.com>]

I am trying to setup a Linux workstation (Slackware 8 with 2.4.18 kernel) to
tie a local network (192.168.x.x) of XP machines to our corporate network.
The Linux machine has a hard coded IP address and it works on the network as
far as telnet, ssh, browsing, etc. We need to have network connectivity from
the XP (for all of those M$ updates) machines through the Linux machine.

I have tried several variations of iptables configurations and it appears
that I still have some NAT problems. On a ping test I appear to have name
resolution, but I don't get any acknowledgements and the browser cannot load
any pages. I have rebuilt the kernel with the following modules:
config_ip_advanced_router
config_ip_nf_iptables
config_ip_nf_filter
config_ip_nf_nat
config_ip_nf_nat_needed
config_ip_nf_target_masquerade
config_ip_nf_target_redirect
config_ip_nf_ftp
config_ip_nf_mangle

Our public interface is eth0 and the private is eth1. eth1 is up and running
with an entry in the route table.

I have followed several tutorials from web sites and books without success.
Also, when I configure the iptables, the Linux machine can no longer browse
internet from the console.

The configuration I have most recently used is:
iptables --table nat --append POSTROUTING --out-interface eth0 -j MASQUERADE
iptables --append FORWARD --in-interface eth1 -j ACCEPT

The references I have used are:
http://www.yolinux.com/TUTORIALS/LinuxTutorialNetworking.html#ADDNIC
http://www.netfilter.org/unreliable-guides/NAT-HOWTO/ 
Linux Firewalls by Robert L. Ziegler

One thing that has not been very clear is if I need to setup ipchains. The
yoliux reference shows the setting of ipchains but none of the other
references talk about using ipchains.

I would appreciate any help or suggestions.
Thanks
Scott Ziegler


 <<Ziegler, Scott.vcf>> 

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