Reinstall OpenSSH Server

First if you have any pre-installed SSH server that has gone bad, remove it-

on Redhat Architechture

Type the following commands as the root user:

# chkconfig sshd off
# service sshd stop
# yum erase openssh-server

You need to edit and update firewall rules that allows inbound connections to SSHs tcp port # 22. Edit /etc/sysconfig/iptables and /etc/sysconfig/ip6tables. In each file find and delete the line that access connection to port # 22. A sample entry:

-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT

Save and close the file. Restart the Linux firewall:

# service iptables restart
# service ip6tables restart

On Debian Architechture

Type the following commands:

# apt-get –purge remove openssh-server

Again, you need to edit and update firewall rules or firewall shell scripts that allows inbound connections to SSHs tcp port # 22.

Now it's time to install the SSH package again, reference installation for Redhat Architechture only

To install the server and client type:

# yum -y install openssh-server openssh-clients

Start the service:

# chkconfig sshd on
# service sshd start

Make sure port 22 is opened:

# netstat -tulpn | grep :22

Firewall Settings
Edit /etc/sysconfig/iptables (IPv4 firewall),

# vi /etc/sysconfig/iptables

Add the line

-A RH-Firewall-1-INPUT -m state –state NEW -m tcp -p tcp –dport 22 -j ACCEPT

Src:

http://www.cyberciti.biz/faq/howto-unix-linux-remove-delete-opensshd-server/