| 3.1 |  | Configuring a Router |
| 3.1.5 |  | Configuring a serial interface |

| A serial interface can be configured from the console or through a virtual terminal line. To configure a serial interface follow these steps: Enter global configuration mode Enter interface mode Specify the interface address and subnet mask Set clock rate if a DCE cable is connected. Skip this step if a DTE cable is connected. Turn on the interface Each connected serial interface must have an IP address and subnet mask if the interface is expected to route IP packets. Configure the IP address using the following commands: Router(config)#interface serial 0/0 Router(config-if)#ip address <ip address> <netmask> Serial interfaces require a clock signal to control the timing of the communications. In most environments, a DCE device such as a CSU will provide the clock. By default, Cisco routers are DTE devices but they can be configured as DCE devices. On serial links that are directly interconnected, as in a lab environment, one side must be considered a DCE and provide a clocking signal. The clock is enabled and speed is specified with the clock rate command. The available clock rates in bits per second are: 1200, 2400, 9600, 19200, 38400, 56000, 64000, 72000, 125000, 148000, 500000, 800000, 1000000, 1300000, 2000000, or 4000000. However, some bit rates might not be available on certain serial interfaces depending of their capacity. By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no shutdown is entered. If an interface needs to be administratively disabled for maintenance or troubleshooting the command shutdown is used to turn off the interface. In the lab environment, the clockrate setting that will be used is 56000. The commands for setting a clock rate and enabling a serial interface are as follows: Router(config)#interface serial 0/0 Router(config-if)#clock rate 56000 Router(config-if)#no shutdown
| Lab Activity Lab Exercise: Configuring a Serial Interface In this lab, the student will configure a serial interface on the Lilongwe and DarEsSalaam routers so they can communicate.
| Lab Activity e-Lab Activity: Configuring a Serial Interface This lab is to access the router command-line interface and activate privileged level configuration options.
| Web Links Configuration http://www.cisco.com/en/US/products/hw/ modules/ps3129/products_tech_ note09186a00800b1502.shtml#fifth