Собственно говоря запишу на память:
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
# The loopback network interface
auto lo
iface lo inet loopback
pre-up iptables-restore < /etc/iptables.up.rules
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [33:5168]
-A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
-A INPUT -p icmp -j ACCEPT
-A INPUT -i lo -j ACCEPT
-A INPUT -s x.x.x.0/24 -j ACCEPT
-A INPUT -s x.x.x.0/24 -j ACCEPT
-A INPUT -j REJECT --reject-with icmp-host-prohibited
-A INPUT -j DROP
-A FORWARD -j REJECT --reject-with icmp-host-prohibited
COMMIT