CentOS/RHEL: How to Open Port in Linux Firewall

This post will guide you how to open a port in CentOS/RHEL Linux. How do I open a port in the firewall on CentOS/RHEL Linux system. How to open tcp ports 80 and 443 in your Linux system.

• Open TCP Port 80/443 on CentOS/RHEL 5/6
• Open TCP Port 80/443 on CentOs/RHEL 7 /8
• Check Current Firewall Rules on CentOs/RHEL

Open TCP Port 80/443 on CentOS/RHEL 5/6

On CentOs/RHEL 5/6, you can use iptables command to add one firewall policy to open a TCP port. Or you can modify the iptables configuration file to add firewall rules.

Type the following commands to open TCP port 80 and 443:

# iptables -I INPUT -p tcp -m tcp -dport 80 -j ACCEPT
# iptables -I INPUT -p tcp -m tcp -dport 443 -j ACCEPT
# service iptables save

Then you need to restart the iptables service, type:

# service iptables restart

You can also add one new firewall rule into iptables configuration file located in /etc/sysconfig/iptables to open a port in your current CentOS/RHEL 4/5/6 Linux. Do the following steps:

#1 edit file /etc/sysconfig/iptables via vi/vim text editor.

# vi /etc/sysconfig/iptables

#2 appending the following line:

-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 443 -j ACCEPT

#3 save and close the file.

#4 restart iptables service, type:

# service iptables restart

Or

# /etc/init.d/iptables restart

If you need to open other tcp ports, you just change the above port as you need.

Open TCP Port 80/443 on CentOs/RHEL 7 /8

For CentOS/RHEL 7 Linux, the firewall rule settings are managed by firewalld service damemon. and if you want to open a tcp port, you need to use firewall-cmd command to achieve it. To open tcp ports 80 and 443, just use the following commands:

# firewall-cmd --zone=public --add-port=80/tcp --permanent
# firewall-cmd --zone=public --add-port=443/tcp --permanent
# firewall-cmd --reload

Then you need to restart firewalld service, type:

# systemctl restart firewalld.service

Outputs:

[root@osetc ~]# firewall-cmd --zone=public --add-port=80/tcp --permanent
success
[root@osetc ~]# firewall-cmd --zone=public --add-port=443/tcp --permanent
success

[root@osetc ~]# firewall-cmd --reload
success
[root@osetc ~]# systemctl restart firewalld.service

If you want to check if those two tcp ports are opened.Just use the following command:

# firewall-cmd --list-port

Outputs:

[root@osetc ~]# firewall-cmd --list-port
443/tcp 80/tcp

From the above outputs, we’ll see that both 80 and 443 ports are opened.

Check Current Firewall Rules on CentOS/RHEL

If you want to check current firewall rules on your centos or RHEL Linux, you can type the following command:

# iptables -L

Outptus:

[root@osetc ~]# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
ACCEPT all -- anywhere 192.168.1.1
ACCEPT all -- anywhere anywhere
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED
ACCEPT all -- anywhere anywhere
INPUT_direct all -- anywhere anywhere
INPUT_ZONES_SOURCE all -- anywhere anywhere