Checking And Assigning IP Address’s To Cisco Router Interfaces-(Fast Ethernet & Serial Interface)

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Cisco Router Interfaces:

In this cisco ccna lab we will explore and configure fast Ethernet interfaces and serial interfaces. For CCNA exam and network administration perspective it is necessary to know all the interfaces of a Cisco router and its configurations. Checking router interfaces play a great role in troubleshooting which often results in solving the connectivity problem by correcting the misconfigured interfaces of router. It is the responsibility of network engineer to monitor all the interfaces of a router for maintaining smooth functionality of the network.

Command for displaying all interfaces of a Cisco router is “show ip interface brief”

UPAAE > enable                               // for executing this command you need to be in enable mode.

UPAAE # show ip interface brief

Assigning IP Address to Cisco Fast Ethernet Interface of Cisco Router:

In the above screenshot you have seen that none of the interfaces are configured, for assigning IP Address to a fast Ethernet port you have to be in global configuration mode. At global configuration mode enter this command “interface fa 0/0”.

This command has three parts 1 interface, 2 type of interface, 3 the port number.

The first part of this command is same for Ethernet and serial ports, the second part is where you have to specify whether you are configuring Serial interface or Ethernet interface(in our case we are going to configure IP address for Ethernet interface), “fa” stands for fast Ethernet. In the third part you have to specify the interface/port number in our case we are going to configure Ethernet port number 0/0.

If you don’t know the interface/ port number of your router run this command ”show ip interface brief” and note the specific interface number of concern.

Interface fa 0/0 will take you to the interface configuration mode where IP Address can be assigned to this interface. Follow the screenshot below.

UPAAE> enable
UPAAE# configure terminal
UPAAE(config)# interface fa 0/0
UPAAE(config-if)# ip address 10.1.1.2 255.0.0.0
UPAAE(config-if)# exit
UPAAE(config)#

Assigning IP Address to Cisco Serial Interface of Cisco Router:

Serial interfaces of a cisco router are commonly used for connecting two routers back-to-back locally or connecting to the WAN. If you want to know more about the serial interfaces this will help you setting clock rate on serial interface. You should note that, while connecting two routers, one must act as DTE and the other as DCE. The one configured with clock rate cisco command is called as DCE (Data communication Equipment).

We have explained the difference between DTE and DCE in more detail in what is clock rate and How Set Clock Rate on Serial Interface of a Cisco router. The command syntax for configuration of serial interface is same as the configuration of Ethernet interface but the variables in the command are different, the command structure will be “interface serial 0/0”. For knowing your Cisco router serial port numbers execute this command “show ip interface brief” from enable mode.

Steps for assigning IP address to a serial interface is demonstrated in the following screenshot.

UPAAE> enable
UPAAE# configure terminal
UPAAE(config)# interface serial 0/0/0
UPAAE(config-if)# ip address 151.136.116.22 255.255.0.0
UPAAE(config-if)# exit
UPAAE(config)#

Checking if IP Addresses are Properly Assigned:

I am always here to help, please do ask in comments for any problem regarding this tutorial.

Note: Even after a successful configuration of cisco router interface you will have to enable that interface for making it functional. As you can see in the above screenshot all the interfaces of cisco routers are by default administratively down. Also the students of ccna networking who are are preparing for ccna exam should give this point proper attention.