#!/bin/sh

PATH=/usr/sbin:/sbin:/bin:/usr/bin

#
# delete all existing rules.
#
iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -X

# Always accept loopback traffic
iptables -A INPUT -i lo -j ACCEPT


# Allow established connections, and those not coming from the outside
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -m state --state NEW -i ! eth1 -j ACCEPT
iptables -A FORWARD -i eth2 -o eth1 -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow outgoing connections from the LAN side.
iptables -A FORWARD -i eth1 -o eth2 -j ACCEPT

# Masquerade.
iptables -t nat -A POSTROUTING -o eth2 -j MASQUERADE

# Don't forward from the outside to the inside.
iptables -A FORWARD -i eth2 -o eth1 -j REJECT

# Enable routing.
echo 1 > /proc/sys/net/ipv4/ip_forward



CPU-1:/# ifconfig -a
eth0      Link encap:UNSPEC  HWaddr 00-11-D8-00-00-AC-E4-D9-00-00-00-00-00-00-00-00
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

eth1      Link encap:Ethernet  HWaddr 00:17:31:9F:C7:62
          inet6 addr: fe80::217:31ff:fe9f:c762/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:69 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:13469 (13.1 KiB)  TX bytes:492 (492.0 b)
          Interrupt:74

eth2      Link encap:Ethernet  HWaddr 00:17:31:9F:CA:1E
          inet addr:12.219.50.87  Bcast:255.255.255.255  Mask:255.255.248.0
          UP BROADCAST RUNNING MULTICAST  MTU:576  Metric:1
          RX packets:140643 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4323 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:9410306 (8.9 MiB)  TX bytes:477489 (466.2 KiB)
          Interrupt:233 Base address:0xc000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:218 errors:0 dropped:0 overruns:0 frame:0
          TX packets:218 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:12788 (12.4 KiB)  TX bytes:12788 (12.4 KiB)

sit0      Link encap:IPv6-in-IPv4
          NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

CPU-1:/#