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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:
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:
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:
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