Linux Firewall with iptables and firewalld

In this article will be covering details regarding iptables and firewalld which helps in Linux firewall management. We will also be looking at how to enable specific ports (1521 for Oracle) inside iptables.

Managing Linux Firewall

The Linux firewalld command will let you check Linux firewall status. It will show you the current status Active in case firewall is running

systemctl status firewalld

To disable firewall immediately and stop it starting from the next reboot

service firewalld stop
systemctl disable firewalld

To enable firewall instantly and start is automatically from next reboot

service firewalld start
systemctl enable firewalld

Enable Ports in Linux

On some servers, port 1521 will not be enabled by default because of security reasons. You can enable this specific port inside linux using below commands.

If you are working on Oracle Linux 5 or 6 version, use Linux iptables command to enable specific ports as root user

iptables -I INPUT -p tcp --dport 1521 -j ACCEPT

If you would like to open any specific port in Linux, just replace the port number (1521) with new port number. To open multiple port ranges in Linux, use below command

iptables -A INPUT -p tcp -m multiport --dports 7101:7200,4889:4898,1159,4899:4908,7788:7809,3872,1830:1849 -j ACCEPT

In some Linux versions, below command works fine

firewall-cmd  --permanent --add-port=1521/tcp