When you configure a router to connect to a network through a serial interface, the router must be connected to a device (such as a CSU/DSU or another router) that provides clocking signals. When you configure two routers in a back-to-back configuration through their serial ports, one router interface must be configured to provide the clocking signals for the connection.
- The router providing clocking is known as the DCE (data circuit-terminating equipment).
- The router not providing clocking is known as the DTE (data terminal equipment).
The DCE interface is identified in two ways:
- The cable connecting the two routers has both a DCE and a DTE end. Connect the DCE end of the cable to the interface you want to be the DCE device.
- The DCE interface is configured to provide a clocking signal with the clock rate command. If the clock rate command is not issued, clocking is not provided, and the line between the two routers will not change to up.