Linux system, use firewall iptables to open and close ports tutorial

In Linux systems, firewall iptables is generally used to control port access. Applicable to centos, debian and other systems.

There are 2 methods in total, just choose one of the following.

All operate under SSH.

1. Command mode:

Allow external network access to port 3306

/sbin/iptables -I INPUT -p tcp --dport 3306 -j ACCEPT #Open port 3306

Close external network access port 3306

/sbin/iptables -A INPUT -p tcp --dport 3306 -j DROP #Close the port

Save and restart the service

/etc/rc.d/init.d/iptables save #Save configuration /etc/rc.d/init.d/iptables restart #Restart the service netstat -anp|grep 3306 #Check whether the port is open

2. Edit the iptables file and add a line below the 22 port location

vi /etc/sysconfig/iptables

After adding it, it will look like this:

##################################### # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state –state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT -A INPUT -m state –state NEW -m tcp -p tcp –dport 3306 -j ACCEPT -A INPUT -j REJECT –reject-with icmp-host-prohibited -A FORWARD -j REJECT –reject-with icmp-host-prohibited COMMIT

Finally restart the firewall to make the configuration take effect

/etc/init.d/iptables restart

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