Router interface Configuration and Verify Configuration

For Ethernet interface configuration you need to make a physical connection to the router Ethernet Interface. However, when establishing a connection, you can proceed with the basic configuration of Ethernet, Fast Ethernet, or Gigabit Ethernet interfaces.

Connecting To Your Router

After connecting to a router you need to get into the Global Configuration Mode  of your router using the following commands:

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 devices in current IOS versions are numbered for example.

  • Gigabit Ethernet interfaces– GigabitEthernet 0/0 (G0/0), GigabitEthernet 0/1 (G0/1)
  • A serial WAN interface card (WIC) interfaces– Serial 0/0/0 (S0/0/0) and Serial 0/0/1 (S0/0/1)

Interface Configuration

For example, we want to configure the FastEthernet 0/0 interface. We should enter the interface mode of  FastEthernet 0/0 using the following command.

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 Internal Interface

Setting IP Address To Interface

Now you did all prerequisites before adding IP address. You can now add IP address to this interface.

Router(config-if)#ip address 192.168.1.1 255.255.255.0

Enabling Your Interface

Before using the router interface you also need to enable the router interface. You 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

There are several commands that can verify interface configuration. For example, the show IP interface brief is the most useful command for verifying interface configuration. The output of this command display all interfaces with their IPv4 address, and also their 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, you can verify the configuration of interface from 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, its 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 This command displays statistics for all interfaces on the device.
  • Ping  This command generated five exclamation marks verifying connectivity to the remote side.
  • show IP interface brief Displays the IPv4 statistics for all interfaces on a router.
  • Show running-config-.This command displays the entire configuration of the router. Here we also need to see the router section in the configuration file to verify the interface configuration.
  • Show startup-config:- When the configuration is saved with the write command, the configuration can be verified by the help of this command.
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