Redhat / CentOS / Fedora Linux Open TCP/UDP Ports

in Categories , , , last updated January 5, 2018

I have Red Hat Enterprise Linux 5 server with Iptabeles firewall enabled. I have started all services but don’t know how to open port using iptables. By default it is only allowing port ssh tcp port # 22. How do I open port 80 / 143 / 110 on Linux?

By default iptables firewall stores its configuration at /etc/sysconfig/iptables file on a RHEL/CentOS 5.x/6.x. You need to edit this file and add rules to open port number. This file only available under:

  1. Red Hat Enterprise Linux 3 / 4 / 5 and 6
  2. Old Red hat Linux version
  3. CentOS 4/5/6
  4. Older version of Fedora Linux

Let us see how to open a port in the firewall on CentOS or RHEL version 5.x/6.x and 7.x including the latest version of Fedora Linux 27 or above.

How to open TCP port 80 on a RHEL/CentOS Linux

Open flle /etc/sysconfig/iptables:
# vi /etc/sysconfig/iptables
Append rule as follows:
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
Save and close the file. Restart iptables:
# /etc/init.d/iptables restart

Open port TCP port # 110 on a RHEL

Append rule as follows:
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 110 -j ACCEPT

Open port 143 on a CentOS

Append rule as follows:
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 143 -j ACCEPT

Restart iptables service

Type the following command:
# service iptables restart

A note about opening a port on CentOS/RHEL 6

You can also use the iptable command as follows to open port 443:
# iptables -I INPUT -p tcp -m tcp --dport 443 -j ACCEPT
# service iptables save

A note about Red Hat Enterprise Linux 7.x and CentOS 7.x

Above commands or files won’t work on RHEL/CentOS 7.x or the latest version of Fedora Linux. To see current open ports, type:
# firewall-cmd --list-ports
Find list of zones:
# firewall-cmd --get-zones
Sample outputs:

block dmz drop external home internal public trusted work

To find about interface name use ip command:
$ ip a
Sample outputs:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1460 qdisc pfifo_fast state UP qlen 1000
    link/ether 42:01:0a:80:00:04 brd ff:ff:ff:ff:ff:ff
    inet brd scope global dynamic eth0
       valid_lft 79076sec preferred_lft 79076sec
    inet6 fe80::4001:aff:fe80:4/64 scope link 
       valid_lft forever preferred_lft forever

To get info about eth0 interface:
# firewall-cmd --get-zone-of-interface=eth0
Sample outputs:


Type the following command to open TCP port 80 for Apache/httpd server:
# firewall-cmd --permanent --add-port 80/tcp
To list open port again, type:
# firewall-cmd --list-ports
Sample outputs:

1191/tcp 80/tcp 22/tcp

To open port range between 2000-3000/tcp, enter:
# firewall-cmd --permanent --add-port 2000-3000/tcp
Command to start/stop/restart firewall:
# systemctl start firewalld
# systemctl stop firewalld
# systemctl restart firewalld
# systemctl status firewalld

Sample outputs:
How to open a port in the firewall on CentOS or RHEL

Verify that port is open

Run following command ss command/netstat command:
# netstat -tulpn | less
# ss -tulpn | less
Make sure iptables is allowing port 80 / 110 / 143 connections by listing rules:
# iptables -L -n -v
Please refer to iptables man page for more information about iptables usage and syntax:
man iptables
man firewall-cmd

See also

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.

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45 comment

  1. Save and close the file. Restart iptables:
    # /etc/init.d/iptables restart

    How to close and save a file?????

    1. LOL, if you can’t even navigate in a *nix environment why do you even bother with iptables?

      nevertheless you can do the following:

      1-insert rules you want
      2- press Esc
      3- press :
      4- wq
      5- Enter

  2. -A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 587 -j ACCEPT

    hi i used this code in fedora 5 to open up the port 587 in my firewall so sendmail would work using this vi command below:

    vi /etc/sysconfig/iptables

    then i applied the changes and restarted the firewall as you metioned above, ok poped up for all selections. did i do this ok? let me know and thanks. rich.

  3. I wonder what is happening on my newly installed centos5.2 as all connections excepts icmp are periodically refused (up and down in un-orderly fashion)

    Please advice whats wrong; action taken
    #service iptables stop
    #chkconfig iptables off
    #chkconfig –del iptables
    #mkdir /backup
    #mv /etc/init.d/iptables /backup/
    #mv /etc/init.d/ip6tables /backup/
    #init 6

    Yet the connection refuse error keep on happening time to time(more frequently that connected)

  4. Sam,

    You must be using another firewall script such as apf. Most hosting companies install something like this.

  5. An application that I use has an in-built Tcl webserver that uses ports 8015/8016. Is there a way to open these ports but at the same time restrict access to only selected IP addresses?

  6. Sweet! I needed to open a port for the Sybase database server I installed on this box. Your instructions worked perfectly. Thanks for taking the time to post these instructions.


  7. Or, you can just run “system-config-securitylevel” and do it the easy way. :)
    I always hated iptables commands.

  8. I don’t seem to have a file called iptables.

    When I create it in /etc/sysconfig and add one of those lines at the top, I get an error upon restart saying

    “Applying iptables firewall rules: iptables-restore: line 1 failed”

    Deleting that file again and restarting the service works fine. Any ideas?

    1. Add your lines, ensuring that they appear before the final LOG and DROP lines for the RH-Firewall-1-INPUT chain. Do not add them at the top of the file.

      1. For me, I needed to change the word RH-Firewall-1-INPUT to simply INPUT – I have CentOS 6.4. So, I ended up adding:

        -A INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT

  9. Thanks Vivek–

    I found that by using “iptables -F” followed by “service iptables save” I can generate this file. It then contians several rules – however LOG and DROP are not mentioned.

    I’ve tried to add the lines in various places but get an error every time. I’m trying to accept incoming UDP traffic on a couple of ports for use with OSSEC.

  10. the script line you advised for opening port 80 didn’t work for me!
    this worked

    -I INPUT -p tcp –dport 80 -j ACCEPT

    1. Yup me too – needed to change RH-Firewall-1-INPUT to just INPUT

      -A INPUT -m state –state NEW -m tcp -p tcp –dport 80 -j ACCEPT

  11. I am Trying To Install Camfrog Server ( Linux Version ) On My Linus CentOS I can Wget And Install The App But Is Stuck After This Point Does Anyone KNow How to Install This App?

  12. Hi iam totally a newbie to Linux, in my office i am assigned to this task which is install redhat enterprise server 5 and open up the ports 21,22 and 23 to someone else to access the box, he also needs to export the display to his machine as well, as this sounds “GREEK” to me, i need help from you guys to get this completed. pls tell me step by step what should i do?

  13. i need to access java web service which is running on Apache in linux at port 8080 from windows.

  14. /etc/sysconfig/iptables-config: line 42: -A: command not found
    /etc/sysconfig/iptables-config: line 43: -A: command not found

    I am getting this error ????

  15. someone from outside my network is failing to access my linux server via SSH but i can access it using Putty from within my network. Nothing has changed on my router and there is no firewall in place to block the SSH connection, how can i allow that connection, the guy can ping the server and access other ports.

  16. This information was very useful/handy to me today (2011-07-14) , 5 years after you wrote this article (SEPTEMBER 13, 2007) ! Thank you so much VIVEK GITE. Please keep posing such useful stuff. Regards.

  17. I edited my /etc/sysconfig/iptables file. adding in the ports I needed to open. I successfully saved and closed the file, verifying the ports were added to file by viewing the iptables file. I then went to restart it with commands listed above. I kept getting command not found. The first line of the file reads: # Firewall configuration written by system-config-securitylevel
    I am running RH Linux 2.6.18-53.el5. How do I stop and start the iptables process so the additional ports will take effect?

  18. Can somebody help me? im trying these methods and they dont work

    iptables: Setting chains to policy ACCEPT: filter [ OK ]
    iptables: Unloading modules: [ OK ]
    iptables: Applying firewall rules: iptables-restore: line 10 failed
    [root@ sysconfig]# nano iptables

    and this is what i have in the file

    # Generated by iptables-save v1.4.7 on Fri Sep 16 10:50:02 2011
    :INPUT ACCEPT [0:0]
    :OUTPUT ACCEPT [13:1276]
    -A INPUT -p icmp -j ACCEPT
    -A INPUT -i lo -j ACCEPT
    -A INPUT -p tcp -m state –state NEW -m tcp –dport 22 -j ACCEPT
    -A INOUT -p tcp -m state –state NEW -m tcp –dport 80 -j ACCEPT
    -A INPUT -j REJECT –reject-with icmp-host-prohibited
    -A FORWARD -j REJECT –reject-with icmp-host-prohibited
    # Completed on Fri Sep 16 10:50:02 2011

  19. There was a TYPO my bad but i still cant get port 80 to listen.

    iptables: Flushing firewall rules: [ OK ]
    iptables: Setting chains to policy ACCEPT: filter [ OK ]
    iptables: Unloading modules: [ OK ]
    iptables: Applying firewall rules: [ OK ]
    [root@ sysconfig]# telnet localhost 80
    Trying ::1…
    telnet: connect to address ::1: Connection refused

  20. Dear All,

    I have installed a sever with CentOS 6.0 and then installed mySQL and PHP in it. Then i installed CPanel in it. After rebooting the system, my Login screen is disabled and i can only login via Putty software on port 22 , and can only see a console screen.
    My question is:
    How can i gain access to my cpanel ? i read in articles that cpanel is accessed via 2082 and 2083 ports. But both are seemed to be blocked.

    Thanks in advance. Please help

  21. Unless I am mistaken/wrong, Fedora 20 does not appear to have the /etc/sysconfig/iptables file. Locally (Fedora 20), I find of similar appearance an /etc/sysconfig/iptables-config file; the append steps listed in this article do not appear to logically fit the syntax of the /etc/sysconfig/iptables-config file.

    Will someone correct me, or may I put in a request for an updated version of this article? Many thanks!!

  22. Sir You save my life using this command
    “-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 143 -j ACCEPT”

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