Three applications of Linux Firewall

Linux firewall's three applications-Linux Enterprise applications-Linux server application information. The following is a detailed description. [Guide] The iptables command is used to filter packets and perform NAT Network Address Translation as shown in the following man queries. This command is widely used, many applications on the network can be implemented.

The iptables command is used to filter packets and perform NAT Network Address Translation (Network Address Translation) as seen in man queries. This command has many applications, many applications on the network can be implemented.

Iptables-administration tool for IPv4 packet filtering and NAT

Application 1: allow computers on the regional network to share bandwidth (NAT) with a real IP Address)

Required devices: One Linux server and two network cards

Nic 1: eth0, use real IP address, Nic 2: eth1, use 192.168.1.254

Set: 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 on the regional network to share bandwidth (NAT) with an ADSL)

This example is very similar to the previous example, but a certain setting must be modified.

Required devices: One Linux server and two network cards

Nic 1: eth0, use real IP address, Nic 2: eth1, use 192.168.1.254

Set: 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


Application 3: allow external computers to access a server in the region Network)

This method protects internal servers.

Required devices: One Linux server and two network cards

Nic 1: eth0, use real IP address, Nic 2: eth1, use 192.168.1.254

Set: 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

Iptables-t nat-a prerouting-I eth0-p tcp-d real IP -- dport 80-j DNAT -- to-destination 192.168.1.13: 80