Linux iptables gateway configuration and port forwarding

[Root @ localhost ~] # Vi/usr/local/bin/firewall. Sh
Echo 1>/proc/sys/NET/IPv4/ip_forward

Modprobe ip_tables
Modprobe iptable_filter
Modprobe iptable_nat
Modprobe ip_conntrack
Modprobe ip_conntrack_ftp
Modprobe ip_nat_ftp

Iptables-F Input
Iptables-F forward
Iptables-F postrouting-T Nat
Iptables-P forward drop
Iptables-T Nat-A postrouting-O eth1-s 192.168.168.0/24-J Masquerade
Iptables-a forward-I eth1-M state -- State established, related-J accept
Iptables-a forward-s 192.168.168.0/24-J accept

# Eth1 is Internet, and 3389 is forwarded to 192.168.168.23
Iptables-T Nat-A prerouting-I eth1-P TCP -- dport 3389-J DNAT -- To 192.168.168.23: 3389
Iptables-a forward-I eth1-P TCP -- dport 3389-D 192.168.168.23-J accept

[Root @ localhost ~] # Echo "/usr/local/bin/firewall. Sh">/etc/rc. Local