From mboxrd@z Thu Jan  1 00:00:00 1970
From: Guillermo Calvo <guillermocalvo@datacenter1.com>
Subject: ipsec nat and iptables
Date: Thu, 25 Aug 2005 11:31:02 -0400
Message-ID: <430DE436.5000200@datacenter1.com>
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Hello

I'm trying to setup a network to network vpn using native ipsec support 
on Centos 4.1


Network A
eth0=  conected to internet
eth1= conected to private lan 192.168.1.1

Network B
eth0 conected to Internet
eth1= conected to private lan 192.168.2.1

>From server A I'm able to ping 192.168.2.1 and viceversa but computers 
in the private lan can't see the other side

I'm using pre-shared keys also I set nat_transversal in racoon

Also I set my servers like iptables router
iptables -A INPUT -m state --state INVALID -j DROP
iptables -A FORWARD -m state --state INVALID -j DROP
iptables -A OUTPUT -m state --state INVALID -j DROP

iptables -A FORWARD -i eth1 -o eth0
iptables -A FORWARD -i eth0 -o eth1

iptables -P INPUT DROP
iptables -P FORWARD DROP

iptables -A INPUT -i eth0 -j ACCEPT
iptables -A INPUT -i ethY -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE


Thanks in advance

Guillermo Calvo