iptables configuration

eth0 outside 192.168.1.x eth1 inside 192.168.2.x

*filter

:INPUT ACCEPT [0:0]

:FORWARD ACCEPT [0:0]

:OUTPUT ACCEPT [0:0]

-A FORWARD -d 192.168.1.1/32 -i eth1 -o eth0 -p udp -m udp --dport 53 -j ACCEPT

-A FORWARD -i eth1 -o eth0 -p tcp -m tcp --dport 25 -j ACCEPT

-A FORWARD -s 192.168.1.1/32 -i eth1 -o eth0 -p udp -m udp --sport 53 -j ACCEPT

-A FORWARD -i eth1 -o eth0 -j DROP

COMMIT

*nat

:PREROUTING ACCEPT [0:0]

:INPUT ACCEPT [0:0]

:OUTPUT ACCEPT [0:0]

:POSTROUTING ACCEPT [0:0]

-A POSTROUTING -o eth0 -j MASQUERADE

-A POSTROUTING -o eth0 -j MASQUERADE

COMMIT