Telnet is an application layer protocol that enables a network administrator to access and manage remote devices. A user on a client machine can utilize software, also known as a Telnet client, to access the command-line interface of another remote machine running a Telnet server program.
A network administrator can access the device by connecting via Telnet to the IP address or hostname of a remote device. Upon connection, the network administrator will be presented with a virtual terminal capable of interacting with the remote host. While Telnet doesn’t offer the same level of security as SSH, it’s still useful in various scenarios where security concerns are mitigated or network segmentation is enforced.
In this blog post, we’ll explore two methods of configuring Telnet on a Cisco router in packet tracer.
Network Topology
Our network setup consists of a router (R1) connected to a PC.
The objective of this configuration is to establish secure communication between the router and the PC using Telnet.
How to Configure Telnet on a Cisco Router
There are two methods of configuring Telnet on a Cisco route. Type 1 uses a username and password, and Type 2 uses only a password.
Let’s walk you through the steps to configure each of these methods on a Cisco router.
Method 1
This method uses both password and username to secure connection to the router.
Here are steps to complete the configuration using method 1;
Step 1: Configure Router’s Interface
R1(config)#interface ethernet0/0
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown
Step 2: Configure Telnet on the router
R1(config)#line vty 0 4
R1(config-line)#transport input telnet
R1(config-line)#password 123456
R1(config-line)#login
R1(config-line)#exit
R1(config)#enable secret 0000000000
Here’s a brief explanation for each of the commands used in the step above;
- R1(config)#line vty 0 4: This command enters the configuration mode for the virtual terminal (VTY) lines on the router. VTY lines are used for remote access to the router over various protocols, including Telnet. The “0 4” specifies the range of VTY lines being configured, from 0 to 4, which allows for up to five concurrent Telnet sessions.
- R1(config-line)#transport input telnet: This command configures the VTY lines to accept incoming Telnet connections only. By specifying “telnet” as the transport input protocol, the router restricts remote access to Telnet sessions, ensuring that only Telnet connections are permitted on these lines.
- R1(config-line)#password 123456: This command sets a password for Telnet access on the VTY lines. Users attempting to establish a Telnet connection to the router will be prompted to enter this password for authentication. In this example, “123456” is used as the password, but you should replace it with a strong, secure password.
- R1(config-line)#login: This command enables login authentication for Telnet access on the VTY lines. When a user attempts to connect via Telnet, the router prompts for a username and password for authentication. The “login” command ensures that login authentication is enforced before granting access.
- R1(config)#enable secret 0000000000: This command sets an encrypted password for privileged EXEC mode access on the router. The “enable secret” password is used to protect access to privileged EXEC mode, which allows users to execute privileged commands and make configuration changes. In this example, “0000000000” is used as the enable secret password, but you should replace it with a strong, secure password.
Step 3: Configure PC’ interface
Step 4: Test Telnet connection
C:\>telnet 192.168.12.1
User Access Verification
Username: admin
Password: 12345
Method 2
This method uses only password to secure connection to the router. Create another network topology as the one above and run the following configuration.
Step 1: Configure the interface of the Router
R1(config)#interface ethernet0/0
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown
Step 2: Configure Telnet on the Router
R1(config)#line vty 0 4
R1(config-line)#transport input telnet
R1(config-line)#password 123456
R1(config-line)#login
R1(config-line)#exit
R1(config)#enable secret 0000000000
Here is a brief explanation of the command of the above;
- R1(config)#line vty 0 4: This command enters the configuration mode for the virtual terminal (VTY) lines on the router. VTY lines are used for remote access to the router. The “0 4” parameter specifies the range of VTY lines being configured, in this case, from 0 to 4, allowing for up to five concurrent Telnet sessions.
- R1(config-line)#transport input telnet: This command specifies the allowed input protocols for the VTY lines. By setting “telnet” as the transport input protocol, the router permits Telnet connections on these lines. This restricts remote access to only Telnet sessions.
- R1(config-line)#password 123456: This command sets the password required for accessing the router via Telnet. Users attempting to establish a Telnet connection will be prompted to enter this password for authentication. In this example, “123456” is the chosen password, but it should be replaced with a strong, secure password.
- R1(config-line)#login: This command enables login authentication for Telnet access on the VTY lines. When a user attempts to connect via Telnet, the router will prompt them for a username and password for authentication. The “login” command ensures that login authentication is enforced before granting access.
- R1(config)#enable secret 0000000000: This command sets the enable secret password, which is used to protect access to privileged EXEC mode. Privileged EXEC mode allows users to execute privileged commands and make configuration changes. In this example, “0000000000” is the chosen enable secret password, but it should be replaced with a strong, secure password.
Step 2: Configure PC
Step 3: Test Telnet connection to the router
C:\>telnet 192.168.12.1
Trying 192.168.12.1 ...Open
User Access Verification
Password: 123456
R1>enable
Password: 0000000000
Related: How to Configure SSH on Cisco Router
Reference: https://github.com/misterkrittin/CCNA-Labs
I am a passionate Networking Associate specializing in Telecommunications.
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