iptables this directive, as the following query with a man can see, it is used to filter packets and doing NAT Network Address Translation (network address translation), the application of this directive are many, can do a lot of applications for the internet.
iptables - administration tool for IPv4 packet filtering and NAT
Application 1: Let the computer local area network to a real IP to share bandwidth (Implementation of NAT)
Chart:
The necessary equipment: a Linux server, 2 network card
Card 1: eth0, use real IP, LAN 2: eth1, use 192.168.1.254
Setting: In / etc / rc.d / rc.local the following lines written
echo "1"> / proc/sys/net/ipv4/ip_forward
modprobe ip_tables
modprobe ip_nat_ftp
modprobe ip_conntrack
modprobe ip_conntrack_ftp
iptables-t nat-A POSTROUTING-o eth0-s 192.168.1.0/24-j MASQUERADE
Application 2: Let the computer local area network to share bandwidth with an ADSL (Implementation of NAT)
This example, and like the previous example, only one set to make changes
Chart:
The necessary equipment: a Linux server, 2 network card
Card 1: eth0, use real IP, LAN 2: eth1, use 192.168.1.254
Setting: In / etc / rc.d / rc.local the following lines written
echo "1"> / proc/sys/net/ipv4/ip_forward
modprobe ip_tables
modprobe ip_nat_ftp
modprobe ip_conntrack
modprobe ip_conntrack_ftp
iptables-t nat-A POSTROUTING-o ppp0-s 192.168.1.0/24-j MASQUERADE
Application 3: Let the outside world can access the local area network computer unit within the server (implementation relocated, transfer port)
Such practices have the effect of protecting the internal server
Chart:
Necessary equipment: a Linux server, 2 network card
Card 1: eth0, use real IP, LAN 2: eth1, use 192.168.1.254
Setting: In / etc / rc.d / rc.local the following lines written
echo "1"> / proc/sys/net/ipv4/ip_forward
modprobe ip_tables
modprobe ip_nat_ftp
modprobe ip_conntrack
modprobe ip_conntrack_ftp
iptables-t nat-A POSTROUTING-o eth0-s 192.168.1.0/24-j MASQUERADE
iptables-t nat-A PREROUTING-i eth0-p tcp-d real IP - dport 80-j DNAT - to-destination 192.168.1.13:80