Step-by-Step Guide to Configuring Router Interfaces Using Command Line

Routers are essential communication devices that facilitate data transfer between different networks. They function as gateways to the internet, directing traffic to the appropriate destination. To prepare your router for proper operation, you must configure the router interface. The interface is responsible for handling all communication between the router and other devices.

Configuring router interfaces can be done through a Graphical User Interface (GUI) or the Command Line Interface (CLI). This article will focus on the command line, which provides more control and possibilities for customization. So, let’s dive into the step-by-step guide to configuring router interfaces using command line.

Step 1: Access the Command Line Interface

Before you begin configuring the router interface, you must first access the Command Line Interface. Open your command prompt or terminal and type the IP address of your router, followed by the default port 23 or 22 for SSH, as follows:

telnet 23


ssh username@

Depending on your router make and model, the IP address might vary. Consult your router manual for this information.

Step 2: Enter Configuration Mode

Once you have accessed the Command Line Interface, enter Configuration Mode. Type the following command in the Command Line Interface and press Enter:


This command activates the privileged EXEC mode, which grants you access to configure the router. You will need to enter the administrator password to access this mode.

Step 3: Enter Global Configuration Mode

After entering privileged EXEC mode, enter Global Configuration Mode to initiate interface configuration. Type the following command in the Command Line Interface:

configure terminal

This command enables global configuration and allows you to enter configuration commands for your router. While you are in this mode, any changes made will be global and apply to the entire router.

Step 4: Configure the Router Interface

At this point, you are ready to configure the router interface. The interface configuration commands might vary depending on your router. However, some essential things you can configure include IP address, subnet mask, and interface type.

For example, to configure a FastEthernet interface with an IP address of and a subnet mask of, type the following commands:

interface FastEthernet0/0
ip address
no shutdown

You can substitute “FastEthernet0/0” with the name of the interface you intend to configure. Ensure that you spell the interface name correctly.

The “no shutdown” command turns on the interface. You can use the “shutdown” command instead to turn off the interface.

You can also configure more advanced settings using other commands, such as setting the bandwidth of the interface, changing duplex and speed settings, and so on.

Step 5: Save the Configuration Changes

After configuring the router interface, save the changes to the configuration file. This ensures that the changes are retained even after the router restarts or reboots.

Type the following command:

write memory

This command saves the current configuration to non-volatile memory. Any changes made afterward will not take place until you save them.

Step 6: Exit Configuration Mode

Once you have finished configuring the router interface, exit Global Configuration Mode and privileged EXEC mode. Type the following commands:


This command takes you back to the regular Command Line Interface with no configuration privileges.


Configuring router interfaces using the Command Line Interface is straightforward, provided you know the right commands. The six steps outlined above should give you enough guidance to configure your router interface quickly and accurately. Remember to follow each step in sequence and save your changes using the “write memory” command. Setting up good interfaces ensures secure and reliable communication and prevents problems with network performance.

Editor Comments

– The article is informative and comprehensive; it covers all the essential steps of configuring a router interface using the Command Line Interface.
– The writing style is clear and concise, making it easy for readers to understand the process.
– The article could benefit from more examples of different interface types and configurations.
– Proofread the article for correct grammar and punctuation before publishing.


Q1: Can I configure router interfaces from a remote location using the Command Line Interface?

A: Yes, you can configure router interfaces remotely using the Command Line Interface. You need to connect to the router using SSH or Telnet, depending on your router configuration.

Q2: Can I use the same IP address for multiple interfaces on the same router?

A: No, it is not advisable to use the same IP address for multiple interfaces on the same router. Doing so will cause network conflicts, and devices will not communicate correctly.

Q3: Do I need to restart the router after making interface configuration changes?

A: No, you do not need to restart the router after making interface configuration changes. The changes will take effect immediately. However, it is advisable to save the configuration changes to non-volatile memory so that they persist even after the router reboots or shuts down.