Basic application Tutorial of Iptables firewall on Linux

Iptables is commonly used on Linux firewall software, the following to everyone to say iptables installation, clear iptables rules, iptables only open the designated port, iptables shield designated IP, IP segment and unblock, Remove basic applications such as iptables that have been added iptables rules.

1. Install iptables Firewall

If no installation of iptables is required first,CentOS executes:

Yum Install Iptables

Debian/ubuntu Execution:

Apt-get Install Iptables2, clear the existing iptables rules Iptables-f
Iptables-x
IPTABLES-Z3, open specified port # allows local loopback interface (that is, running native access to this machine)
Iptables-a input-s 127.0.0.1-d 127.0.0.1-j ACCEPT
# allow established or connected passes
Iptables-a input-m State--state established,related-j ACCEPT
#允许所有本机向外的访问
Iptables-a output-j ACCEPT
# Allow access to port 22
Iptables-a input-p TCP--dport 22-j ACCEPT
#允许访问80端口
Iptables-a input-p TCP--dport 80-j ACCEPT
#允许FTP服务的21和20端口
Iptables-a input-p TCP--dport 21-j ACCEPT
Iptables-a input-p TCP--dport 20-j ACCEPT
#如果有其他端口的话, the rules are similar, and you can modify the above statements slightly.
#禁止其他未允许的规则访问
Iptables-a input-j REJECT (Note: If the 22 port does not join the Allow rule, the SSH link will be disconnected directly.) ）
Iptables-a forward-j REJECT4, shielding ip# if only want to block the IP words "3, open the specified port" can skip directly.
#屏蔽单个IP的命令是
Iptables-i input-s 123.45.6.7-j DROP
#封整个段即从123.0.0.1 to 123.255.255.254 command
Iptables-i input-s 123.0.0.0/8-j DROP
#封IP段即从123.45.0.1 to 123.45.255.254 command
Iptables-i input-s 124.45.0.0/16-j DROP
#封IP段即从123.45.6.1 to 123.45.6.254 command is
Iptables-i input-s 123.45.6.0/24-j DROP4, view added iptables rule iptables-l-N

V: Show details, including the number of matched packets per rule and the number of matching bytes
x: On the basis of V, Prohibit automatic unit conversion (K, M) VPS Detective
N: Show only IP address and port number, do not resolve IP to domain name

5. Delete the iptables rule that has been added

Displays all iptables as an ordinal tag, executing:

Iptables-l-N--line-numbers

For example, to delete the rule with the number 8 in input, execute:

iptables-d INPUT 86, iptables boot and rule saving

CentOS may exist after installing the iptables, Iptables does not boot from the boot, you can execute:

Chkconfig--level 345 iptables on

Add it to boot.

CentOS can be performed: Service iptables save the rule.

It is also important to note that debian/ubuntu on iptables will not save the rules.

Need to follow the following steps, so that the network card shutdown is to save iptables rules, start loading iptables rules:

Create the/etc/network/if-post-down.d/iptables file and add the following:

#!/bin/bash
Iptables-save >/etc/iptables.rules

Execute: chmod +x/etc/network/if-post-down.d/iptables Add execute permissions.

Create the/etc/network/if-pre-up.d/iptables file and add the following:

#!/bin/bash
Iptables-restore </etc/iptables.rules

Execute: chmod +x/etc/network/if-pre-up.d/iptables Add execute permissions.

More information on how to use iptables can be performed: Iptables--help or search the web for a description of the iptables parameter.

Basic application Tutorial of Iptables firewall on Linux