How to: Allow telnet and ssh through iptables under Linux
Q. I run both RHEL / CentOS Linux server and by default firewall blocked out everything including telnet / ssh access. How do I allow telnet - port 23 and ssh port 22 thought Linux iptables firewall ?
A.By default firewall rules stored at /etc/sysconfig/iptables location / file under CentOS / RHEL. All you have to do is modify this file to add rules to open port 22 or 23.
Login as the root user.
Open /etc/sysconfig/iptables file, enter:
# vi /etc/sysconfig/iptables
Find line that read as follows:
COMMIT
To open port 22 (ssh), enter (before COMMIT line):
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT
To open port 23 (telnet), enter (before COMMIT line):
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 23 -j ACCEPT
Save and close the file. Restart the firewall:
# /etc/init.d/iptables restart
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Tags: centos linux, firewall rules, iptables firewall, linux iptables, open port 22, open port 23, open ssh port, open telnet port
November 27th, 2007 at 8:55 pm
To get fancy with iptables and block repeated failed connection attempts, check out this article:
http://www.itwire.com/content/view/13841/53
May 24th, 2008 at 7:42 am
send me code of linux firewall in C.
May 24th, 2008 at 3:48 pm
http://www.netfilter.org/
June 1st, 2008 at 4:15 pm
Hi,
I don’t think this is not a good idea to allow telnet access nowaday.nobody is using telnet on linux box. Disable this service first
Also it is not a good idea to allow ssh access to everyone over the net
# Permitt SSH access to my ip and my network
/sbin/iptables -A INPUT -s 8.23.2.11 -p tcp –dport ssh -j ACCEPT
/sbin/iptables -A INPUT -s 4.3.8.0/24 -p tcp –dport ssh -j ACCEPT