How to configure Telnet Server in RHEL6

In this article I will configure Telnet Server in RHEL 6. Telnet protocol allows you to connect to remote hosts over TCP/IP network.

Telnet was developed in 1969. Telnet was initially developed for private use where security was not primary concern. Telnet protocol has serious security issue. Security expert recommend that the use of Telnet for remote login should be discontinued under all normal circumstances.

• Telnet Server
• Telnet Client

Telnet Sever

Telnet server software is installed on remote host. You need to configure it before client can connect with it.

Telnet Client

Telnet client software allows you to connect telnet server. Once telnet client establishes a connection to the remote host, client becomes a virtual terminal, allowing you to communicate with the remote host from your computer.

Security issue with Telnet

• Telnet by default does not encrypt any data sent over the connection.
• Anyone who has access to network device located on the network between the two hosts like router, switch, hub or gateway where Telnet is being used can intercept the packets passing by and obtain login, password and whatever else is typed with a packet sniffer software.
• Telnet protocol have no implementations that would ensure that communication is carried out between the two hosts is not intercepted in the middle.

In this tutorial I will configure telnet server in LAB environment. 

• In RHEL Telnet is part of the xinetd daemon.
• Telnet use plain text to transmit password.
• root user is not allowed to connect using Telnet.
• Command-line telnet clients are built into all major operating systems.
• RedHat recommends you to use SSH to connect a system instead of Telnet.
• Use Telnet in LAB environment where security is not concern.

Configure Telnet in RHEL 6

Three RPM are required to configure telnet server in linux.

• xinetd
• telnet-server
• telnet-clinet

Login from root user and check required RPM. If you do not have the telnet-server or telnet packages installed, you can install them with the RPMs available from your installation media. The version numbers of the package should not matter, Red Hat Network (RHN) will always provide you with the latest version of the package.

Once you have the packages installed, check the /etc/xinetd.d/telnet file

ensure that disable = yes is changed to read disable = no.

Turn the Telnet server on using the chkconfig command.

Also check xinetd service

You will need to restart the xinetd service.

As I said above root user is not allowed to login from telnet. We need to create a normal user account.

To connect with telnet server we need specify server IP address which you can check with ifconfig command. You should test telnet configuration before connecting from client computer.

To terminate telnet session logout from logged in user.

Configure telnet client in RHEL6

Go on linuxclient system. linuxclient system have RHEL 6 installed and connected with our server system. Login from root and check telnet and xinetd package

check telnet service status on it if it is set to off

open configuration file of telnet

check telnet service is enabled make sure that disable = yes is changed to disable = no

restart the xinetd service

Check connectivity with server

We are getting reply of ping from server so we have connectivity with server .connect with telnet server

Error

telnet:connect to address 192.168.1.1:No route to host

Telnet client is unable to connect with telnet server because firewall on server is blocking telnet connection. To solve this error Go on server

Run setup command

select Firewall configuration

Firewall is enabled by default

To disable the firewall unselect the enable

Ignore the warning and select OK and press enter

Select Quit and press enter to save the configuration

restart the xinetd service

Now come back to linuxclient system and try to connect with telnet sever

This time we have successfully connected with Telnet server. To terminate telnet session logout from testuser.We have successfully configured Telnet client on RHEL 6.

How configure Telnet client on Window 7

Open command prompt and run telnet command

Error

 'telnet' is not recognized as an internal or external command, operable program or batch file.

You will get error because Window 7 does not turn on telnet client service automatic. We need to start it manually.

Open control panel and click on program.

click on turn windows features on or off

Scroll down and check mark on Telnet client and click on OK

Now you can run telnet command. Login form normal user

logout from normal user and try to login from root

By default root user is not allowed to login through the terminal session

To allow root user Go on server system and open /etc/securetty file

In the end of file add pts/0 and save the file

Go back on windowclient system and try again to login from root user

In this article I have configured Telnet server on RHEL6 system in LAB environment.