3 Applications of Linux firewalls

Iptables this instruction, as shown in the following man query, it is used to filter packets and do NAT network address translation (network location translation), the application of a lot of this directive, can do many network application.

Iptables-administration tool for IPV4 packet filtering and NAT

Application 1: Let the computer in the area network share the bandwidth (real NAT) with a real IP

Schema diagram:

Required Equipment: One Linux server, 2 Web card

Network card 1:eth0, using real IP, network card 2:eth1, using 192.168.1.254

Setting: Write the following lines in/etc/rc.d/rc.local

　　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: Allow computers in the area network to share bandwidth (implemented NAT) with an ADSL

This example is similar to the previous example, just a certain setting to be modified

Schema diagram:

Required Equipment: One Linux server, 2 Web card

Network card 1:eth0, using real IP, network card 2:eth1, using 192.168.1.254

Setting: Write the following lines in/etc/rc.d/rc.local

　　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