Categories
Network protocols

Telnet & SSH

Telnet

Telnet is a network protocol that allows a user to communicate with a remote device. It is a virtual terminal protocol used mostly by network administrators to remotely access and manage devices. Administrator can access the device by telnetting to the IP address or hostname of a remote device.

To use telnet, you must have a software (Telnet client) installed. On a remote device, a Telnet server must be installed and running. Telnet uses the TCP port 23 by default.

One of the greatest disadvantages of this protocol is that all data, including usernames and passwords, is sent in clear text, which is a potential security risk. This is the main reason why Telnet is rarely used today and is being replaced by a much secure protocol called SSH. Here you can find information about setting up Telnet access on your Cisco device.

NOTE
The word telnet can also refer to the software that implements the telnet protocol.

 

On Windows, you can start a Telnet session by typing the telnet IP_ADDRESS or HOSTNAME command:

telnet windows

SSH (Secure Shell)

SSH is a network protocol used to remotely access and manage a device. The key difference between Telnet and SSH is that SSH uses encryption, which means that all data transmitted over a network is secure from eavesdropping. SSH uses the public key encryption for such purposes.

Like Telnet, a user accessing a remote device must have an SSH client installed. On a remote device, an SSH server must be installed and running. SSH uses the TCP port 22 by default.

Here is an example of creating an SSH session using Putty, a free SSH client:

putty

NOTE
SSH is the most common way to remotely access and manage a Cisco device. Here you can find information about setting up SSH access on your Cisco device.

Prerequisites for 200-301

200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers.

The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Solutions (CCNA). The successful completion of a training course will get you a training badge.

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