[lug] nat and proxy firewall rules

[Richard Fifarek]

	To NAT a subnet (192.168.1.0 is internal network, 192.168.2.0 is 
external network):

	iptables -t nat -A POSTROUTING -s 192.168.1.0/255.255.255.0 \ 
-o eth2 -j SNAT --to-source 192.168.2.1



	To do port forward SMTP:

	iptables -t nat -A PREROUTING -d 192.168.2.1 -i eth2 -p tcp \ 
-m tcp --dport 25 -j DNAT --to-destination 192.168.1.X:25 	

	iptables -A FORWARD -d 192.168.2.1 -i eth2 -p tcp -m tcp \
--dport 25 -j ACCEPT

	192.168.2.1 = External IP of NAT machine
	eth2 = External interface of NAT machine
	

	This is by no means the only rules you'll need, but it'll get you 
headed in the right direction.


	For documentation, www.netfilter.org and trial and error.

	For a simple utility that has helped me with templates for 
generating my own rules, see genfw:

	http://www.kspei.com/projects/genfw/

	Hope this helps.

-- 
Richard H. Fifarek
rfifarek at silug.org