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Configuring a Serial Interface : How to Configure the Serial Interface of a CISCO Router

Updated on July 10, 2011

The serial interface of a CISCO router can be configured from the console or through a virtual terminal line. The configuration of a CISCO router is very simple and easy. At first, you have to select the interface and then the IP address. Later, the serial interface may require clock signal if it's a DCE otherwise nothing. This page contains all the information to configure the serial interface of a CISCO router.

Steps to configure the serial interface of a CISCO router:

The steps to configure a CISCO router is described below:

Step 1:

At first, enter the global configuration mode and then enter the interface mode. To enter interface mode, you have to type interface serial 0/1 command. Here, 0/1 means the port no or port slot.Put the serial interface port/port slot according to the desired port you want to configure.

Step 2:

Now, configure the IP address and the subnet mask. Please, careful to use the correct subnet address.

Step 3:

Now, set the bandwidth. It's optional but you may assign now or later.

Step 4:

Set the clock rate if you want to use the router as a DCE. Otherwise, skip this step.

Step 5:

At last, turn on the interface.

Note:

  • By default, the interfaces are turned off. So, to turn on an interface, use no shutdown command. If you don't use this command, your router may not work properly.
  • Always careful about the DTE and DCE. DTE refers to Data Terminal Equipment and DCE refers to Data Communication Equipment. When you are connecting two routers by a cable, then one end must be DCE. If you use both end either DTE or DCE, the router will not work. So, keep special attention whether you need to configure the router as a DCE or DTE. If it needs to configure as DCE, then set the clockrate of that terminal port.

Pracitcal Example of a CISCO Router's Serial Interface Configuration

Let there is a router. We want to configure it's serial port 2/0. The IP address of that port will be 192.168.0.1 and subnet mask will be 255.255.255.0. Moreover, we have to set the bandwidth 120Kb. Configure the router as a DCE.

Router Configuration Command

Router>enable 
Router#configure terminal 
Enter configuration commands, one per line.  End with CNTL/Z.
Router(config)#interface serial 2/0
Router(config-if)#ip address 192.168.0.1 255.255.255.0
Router(config-if)#bandwidth 128
Router(config-if)#clock rate 56000
Router(config-if)#no shutdown 
Router(config-if)#exit
Router(config)#

Discussion of the above command

Before configuring the router, we access the global configuration mode. After accessing global configuration mode, we select the interface which we want to configure by the command interface serial 2/0 and then set the IP address by the command ip address 192.168.0.1 255.255.255.0. Now, set the bandwidth by the command bandwidth 128. As the router is a DCE, the clock rate is set by the command clock rate 56000. At last use the command no shutdown command to up the router.

Test yourself

You have given a CISCO router. You have to configure base on the following specifications:

  • The router will be a DCE and bandwidth will be 256Kb.
  • Assign IP address (172.16.55.1/24 ) on serial 3/0 port

Answer / Solution: Click the following link

Show me the answer of this exercise

© Written by rancidTaste

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    • profile image

      Allah's slave 7 years ago

      Thank you for your efforts in writing this helpful info. about CISCO router. I hope you every success in your life

    • profile image

      Allah's slave 7 years ago

      Thank you for your efforts in writing this helpful info. about CISCO router. I hope you every success in your life

    • profile image

      kosovo 7 years ago

      thnxx so much man

    • profile image

      vadivel 7 years ago

      good basic stuff

    • profile image

      nilesh 6 years ago

      Thank you for your efforts in writing this helpful info

    • profile image

      ARVIND PANWAR 6 years ago

      Router>enable

      Router#configure terminal

      Enter configuration commands, one per line. End with CNTL/Z.

      Router(config)#interface serial 2/0

      Router(config-if)#ip address 192.168.0.1 255.255.255.0

      Router(config-if)#clock rate 64000

      Router(config-if)#no shutdown

      Router(config-if)#exit

      Router(config)#

    • profile image

      salman 6 years ago

      THANKX A LOT

    • profile image

      Alex Paul Kayamba 6 years ago

      Router>enable

      Router#configure terminal

      Enter configuration commands, one per line. End with CNTL/Z.

      Router(config)#interface serial 3/0

      Router(config-if)#ip address 172.16.55.1 255.255.255.0

      Router(config-if)#bandwidth 256

      Router(config-if)#clock rate 56000

      Router(config-if)#no shutdown

      Router(config-if)#end

      Router#wr

    • profile image

      Dale wrangian 4 years ago

      thanks this step helps

    • profile image

      Krishan 4 years ago

      thank you........

    • profile image

      Nufael Nasir 4 years ago

      Hey guys, been working up my blog. I post this kind of cisco stuff too :D

      Check it out: www.itnetcanada.blogspot.com

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