Redhat / CentOS / Fedora Linux Open Port

by Vivek Gite · 11 comments

Q. I’ve Redhat Enterprise Linux 5 server with Iptabeles firewall enabled. By default it is only allowing port 22. How do I open port 80 / 143 / 110 on Linux? I've started all services but don't know how to open port using iptables.

A. By default iptables firewall stores its configuration at /etc/sysconfig/iptables file. You need to edit this file and add rules to open port number. This file only avilable under
Red Hat Enterprise Linux 3 / 4 / 5 and above
=> Old Red hat Linux version
=> CentOS 4 and above
=> Fedora Linux

Open port 80

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 110

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

Open port 143

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

Verify that port is open

Run following command:
netstat -tulpn | less
Make sure iptables is allowing port 80 / 110 / 143 connections:
iptables -L -n

Refer to iptables man page for more information about iptables usage and syntax:
man iptables

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{ 11 comments… read them below or add one }

1 Erion Budo 02.12.08 at 2:24 pm: Save and close the file. Restart iptables: # /etc/init.d/iptables restart
How to close and save a file?????
2 cass 03.19.08 at 7:19 pm: save and close a file in VI
hit ESC
type :
type x

[ESC:X]
3 rich 10.06.08 at 5:28 pm: -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.
4 Sam 12.01.08 at 8:28 am: 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)
5 vivek 12.01.08 at 9:16 am: Sam,

You must be using another firewall script such as apf. Most hosting companies install something like this.
6 Paul 05.01.09 at 12:16 pm: Don’t forget to make sure the ACCEPT lines are before any REJECT lines
7 arijeet maji 05.05.09 at 6:54 am: good site, helped me a lot to restart a port in linux 5
8 Craig 06.10.09 at 5:50 am: 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?
9 Wayne 07.16.09 at 11:33 pm: 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.

Wayne
10 John Dondapati 08.04.09 at 6:06 pm: THank you so much buddy. That really helped.
11 Mikey 11.10.09 at 8:22 am: Or, you can just run “system-config-securitylevel” and do it the easy way. :)
I always hated iptables commands.