Download the Telnet package (for server and client)

# yum install telnet
# yum install telnet-server

Activate Telnet

# vi /etc/xinetd.d/telnet

Change disable=no

Start the Xinetd service

# service xinetd start

Enable Telnet and Xinetd on startup

# chkconfig telnet on
# chkconfig xinetd on

Disable the firewall:

# service iptables stop
# service ip6tables stop
# chkconfig iptables off
# chkconfig ip6tables off

Additional information:

To allow root acces via telnet (not recommended - use at own risk)

# vi /etc/securetty

Add the following at the end

pts/0
pts/1
pts/2
pts/3
pts/4
pts/5
pts/6
pts/7
pts/8
pts/9