Cisco Router Interface Configuration

/ /

A physical connection is necessary for the router’s Ethernet interface configuration. However, when establishing a connection, you can proceed with the basic interface configuration of Ethernet, Fast Ethernet, or Gigabit Ethernet. After connecting to a router, you need to get into the Global Configuration Mode of your router using the following commands:

Interface configuration

The next option is to choose the correct interface. Many different types of interfaces are available on Cisco routers, such as Ethernet, Fast Ethernet, Gigabit Ethernet, and serial interface. All interfaces in IOS are exactly numbered. For example, we want to configure Fast Ethernet, which has a number of 0/0. We should enter the command as shown below.

Router(config)#interface FastEthernet 0/0

Adding a Description to the Ethernet Interface

This feature is not necessary, so you may bypass it. This feature provides a description of the interface, and it does not assist with the configuration. So, it just helps prevent human error.

Router(config-if)#description <Write description of the interface here>

Setting IP Address on Interface

Now you have done everything necessary to add the IP address to the interface. Use the following command to enter an IP address according to your IP scheme to the interface.

Router(config-if)#ip address 192.168.100.1 255.255.255.0

Enabling Interface

Before using the router interface, you also need to enable the corresponding interface. We can enable the router interface by entering the following command.

Router(config-if)#no shutdown
%LINK-5-CHANGED: Interface FastEthernet0/0, changed state to up

Verifying Router Interface Configuration

We can verify interface configuration using several commands. For example, the <show ip interface brief> is the most helpful command for verifying interface configuration. The output of this command displays all interfaces with their IPv4 address and the current status. The configured and connected interfaces should display a status “up” and Protocol “up”. Any other statements would indicate a problem with the configuration or the cabling. Also, remember that show commands are working in “Privileged mode”

In the same way, we can verify the configuration of the interface using <show running-config>  and also with show startup-config. We can also verify connectivity from the interface using the ping command. The ping command sends five consecutive pings and measures minimal, average, and maximum round-trip times. Exclamation marks in Cisco routers also verify connectivity.

Following is the output of the show ip interface brief command, which shows all three router interfaces. FastEthernet  0/0, status is up, and protocol is also up. This interface is connected to other networks, and the protocol is up. FastEthernet status is up, it means that interface is configured and enabled with no shutdown command, its protocol is down, it’s mean that there is something wrong with the cable or some problem from another side. Serial 0/0/0 interface is not configured, not enabled and there is also no IP address assigned to this interface.

Following are other commands that we can use to verify interface configuration.

  • show interfaces– Displays statistics for all interfaces on the device.
  • Ping – Using the ping command, we can generate five exclamation marks verifying connectivity to the remote side.
  • show running-config-.The command shows the entire configuration of the router.
  • show startup-config:- When the configuration is saved with the write command, we can verify it using the command mentioned.