The full name of Telnet protocol is Terminal Network Protocol. Terminal Network protocol is a network protocol used to connect computers remotely to the Internet or Local Area Network.
What is Telnet Protocol?
In other words, the Terminal Network protocol is a client-server protocol With the help of which we can remotely access any other computer from one computer in a worldwide network.
The Terminal Network was developed in 1969. It is defined in RFC 854. Telnet connections are called virtual terminal connections.
This protocol uses TCP network protocols to connect to a computer or host. Telnet service is available on port 23 of a host.
With the help of this protocol, we can access information or run programs without physically going to a host or computer. This also saves our time and also takes less effort.
While terminal network to any computer user, we use his username and password. Once we log in to that computer, we can access it like a local user.
This protocol is considered less safe to use in the public network (Internet). Therefore, it becomes important to use the SSH (Secure Shell) protocol to remotely access a computer in a public network.
SSH protocol is also known to remotely access hosts like telnet but it is more secure than terminal network. It is considered safer to use Terminal Network only and only in private networks (LAN).
Advantages of Telnet Protocol
- Through this, we can send and receive data from one computer to another computer without any problem.
- .This protocol supports user authentication.
- All terminal network clients and servers implement a network virtual terminal (NVT).
- It can be used in almost all types of operating systems.
- This protocol saves a lot of time. Because we do not have to physically go to any host.
- It is very flexible because it can be easily deployed on any computer.
Disadvantages of Telnet Protocol
There is a huge security risk in this terminal network protocol because the username and password are transmitted without any encryption. With this hackers can easily hack our computers and steal information.
- The major drawback of this protocol is that it cannot run GUI-based tools because it is a character-based communication protocol.
- It is a very inefficient protocol.
- Typing speed is very slow when working remotely.
Let us understand telnet with an example:-
“Suppose you have a network administrator in a company. Your company network is huge and has many hosts. The network is so big, that if you have to access all kinds of data from the host or run programs from the host then you have to Will have to go to the host physically.
But because your company’s network is large, you can’t visit every host. Going to each host physical can takes a lot of time and it can also interfere with other employees. In this case, you can use Telnet.
How do you use Telnet Protocol?
Terminal Network is a platform-independent program i.e. it can be run on any platform. To run it, we can also use the windows command prompt (if you want to remotely access a user’s computer from the Windows platform).
Or you can also use the command prompt of the Cisco device. (If you want to remotely access any other Cisco device from a Cisco device.)
To run Terminal Network, we execute the terminal network command. Next to this command, you write the name of the host or the IP address of its computer, which you want to access remotely.
It is being explained by the example below:-
When we want to access a host remotely, before that it is necessary to configure the password on that device. We set this password while configuring that device. If this password is not already configured then you will get the message shown below.
Password required, but none set
If the device we want to access remotely, if its terminal network password has already been configured, then you will be getting the message shown below and will be asked to enter the password.
User Access Verification Password:
In Cisco devices, you can write the IP address of the host directly even without typing the telnet command, and even after doing so, you will be able to access that host remotely. An example of this is given below.
How to check Telnet Connection?
If we want to see the terminal network connections on the network router, then for this we execute the show sessions commands. You can also execute this command on your original router.
This command shows all the lists of your terminal network connections. An example of this is given below.
Router1# show sessions
How to check Telnet users?
If you want to see all those console ports on which telnet connection is running, then for this you can see the show list of all those users by executing the show users command.
An example of this is given below.
Router1# show users
How to terminate Telnet Protocol Sessions?
You can terminate a terminal network connection in 2 ways. If you are in telnetted network router then you can use the exit command. As we know that by using this command you return to the original router and the telnet connection gets terminated.
Suppose network router2 is telneted from terminal network router1 then you will terminate this connection with network router2 like this.
If you want to abort the telnet connection to the original router, you execute the exec command. But thus you need to know the session number to stop the telnet connection.
Any number of telnet connection sessions that you can view with the show session command. Writes your session number after the close command. Examples are given below.
Router1# discontinue 2
In the above example, number 2 session Telnet connection is closed. It does not require you to stop the connection by visiting each telnet device separately.
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