Basic use of Linux firewall iptables

Iptables is a basic component of Linux. It is mainly used in firewall applications, such as banning access to a certain IP or banning some ports to improve website security. Under normal circumstances, the system will install it by default. If it is not installed, you can install it yourself:

yum install iptables #centos system

apt-get install iptables #debian/ubuntu system

1. Let’s talk about some common commands:

service iptables -status #Check whether iptables is running

iptables -F #Capital F, clear all current rules

iptables-save #Note that there is no space between s- to save the current rules

iptables -L -n #List displays current rules

2. Common IP blocking commands:

iptables -A INPUT -s 123.45.67.89 -j DROP #Block a single IP address

#To shield the entire segment (class A address) from 192.0.0.1 to 192.255.255.254, add the following rules.

iptables -I INPUT -s 192.0.0.0/8 -j DROP

#Block the IP segment (Class B address) from 192.168.0.1 to 192.168.255.254, then add the following rules.

iptables -I INPUT -s 192.168.0.0/16 -j DROP

#Block the IP segment (Class C address) from 192.168.200.1 to 192.168.200.254, then add the following rules.

iptables -I INPUT -s 192.168.200.0/24 -j DROP

3. View and delete commands:

iptables -L -n --line-numbers #Display current rules in line list

iptables -D INPUT 15 #Delete rule 15

Please note that after making any modifications, you must save and restart, otherwise they will become invalid.

service iptables save

service iptables restart

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