Cisco Router Interface Configuration

The physical connection is necessary for Ethernet interface configuration of the router. 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. There are many different types of interfaces available on Cisco routers such as Ethernet, Fast Ethernet, Gigabit Ethernet or serial interface. All interfaces in IOS are exactly numbered. For example, we want to configure the Fast Ethernet which number is 0/0. We should enter the command as shown below.

Router(config)#interface FastEthernet 0/0

Adding a Description to Ethernet Interface

This feature is not necessary, so, you may bypass this feature. This feature providing 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 did everything necessary adding 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 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 useful command for verifying interface configuration. The output of this command displays all interfaces with their IPv4 address as well as with the current status. The configured and connected interfaces should display a status “up” and Protocol “up”. Any other statements would indicate a problem with either the configuration or the cabling. Also, remember that show command are working in “Privileged mode

In the same way, we can verify the configuration of interface using <show running-config>  and also with show startup-config. We can also verify connectivity from the interface using the ping command. Ping command send five consecutive pings and measure 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 show all three interfaces of the router. FastEthernet  0/0, status is up and protocol is also up. its mean that this interface is connected to other network and 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.

Cisco Router Interface Configuration 2

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

  • show interfaces– Displays statistics for all interfaces on the device.
  • Ping – Using 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, then we can also verify the configuration using the mentioned command.