Cisco Telnet Configuration: IPv4 And IPv6

In this lesson, we will focus on Cisco Telnet Configuration. We will learn how to configure telnet on Cisco routers. Here, we will focus on how to configure IPv4 telnet on Cisco routers and then we will focus on IPv6 telnet on Cisco routers. Let’s firstly start with what is Telnet?

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What is Telnet stands for?

Telnet is one of the most used protocols in networking. It is a remote access protocol used in computer networks. Telnet is the abbreviation of “telecommunications network”. It is a standard of ISO (International Organization for Standardization). The default port of Telnet is TCP 23 Port. (All Network Ports)

In today’s network world, instead of telnet, SSH is used. SSH (Secure Shell) is more secure than telnet. This is because Telnet is plain-text and SSH is encrypted.

How to Configure Telnet for IPv4 Devices on Cisco Routers?

Network engineers use Telnet and SSH to connect the network devices remotely. To use these protocols, firstly, we should configure them on the routers. Here, we will focus on Cisco telnet configuration to access a device with IPv4 Address.

To use Telnet on a Cisco router, we should configure Telnet on this router. Our IPv4 telnet configuration steps will be like below:

Firstly, we enter 16 telnet sessions from 0 to 15 with “line vty 0 15” command. Before, we could define only 5 sessions with “line vty 0 4” command. But for now, we can define 16 sessions.

Router # configure terminal

Router (config)# line vty 0 15

Then we determine telnet password with “password password” command. To configure telnet password as cisco123, we will use “password cisco123” command.

Router (config-line)# password cisco123

Lastly, to enable remote login, we will use “login” command.

Router (config-line)# login

After IPv4 telnet configuration, we can access this device over telnet. To do this we will use the interface ip address with telnet command like “telnet x.x.x.x”.

To see the active telnet users on a Cisco router, we can use “show users” command.

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How to Configure Telnet for IPv6 Devices on Cisco Routers?

After telnet configuration for IPv4, now, let’s focus on how to configure telnet to access an IPv6 device.

Firstly, we will define a static hostname to address mapping to hostname cache with “ipv6 host name [port] ipv6-address” command. Let’s use “abc” as name and “2001:AAA:0::1” as the ipv6 address.

Router # configure terminal

Router (config)# ipv6 host abc 2001:AAA:0::1

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Secondly, we use “line vty line-number [ending-line-number]” command. Here we will set it for 16 sessions again with “line vty 0 15” command.

Router (config)# line vty 0 15

Then, we will set telnet password with “password password” command. Let’s use “Cisco123” password again.

Router (config)# password Cisco123

After that we will use “login [local | tacacs]” command to enable remote login. We can use also local and tacacs options. Here, we will use only “login local” command.

Router (config)# login local

Lastly, we will use “telnet host” command, to establish a Telnet session from a device to a remote host using either a hostname or an IPv6 address.

Router (config)# telnet abc

After this configuration we can use IPv6 address or the host name to access the IPv6 enabled remote device with telnet. Let’s try with hostname.

Router # telnet abc

Trying abc (2001:AAA:0::1)… Open

User Access Verification

Password:

We can use “show users” command to see the active telnet users on a Cisco router.

Conclusion

In this lesson, we have learned IPv4 and IPv6 telnet configuration on Cisco routers. We have learned IPv4 and IPv6 telnet commands of Cisco devices. Although today SSH is most popular, it is good to know telnet configurations beside SSH configurations.

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