WAN Connection Facts

WAN Connection Facts

Whether ordering a WAN connection from a service provider or configuring a back-to-back router lab, you should know how to connect the devices. There are several different types of cables used in WAN connections and choosing the correct cable largely depends upon identifying the following:

Component	Details
Interface operating mode	When a device communicates over a serial interface, the interface operates in one of the following modes: The interface/device providing clocking is known as the DCE (Data Communications Equipment). The interface/device not providing clocking is known as the DTE (Data Terminal Equipment). 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.
Service	The following WAN service options will also affect which type of cable is needed for a WAN connection: X.25 Frame Relay Asynchronous Transfer Mode (ATM) Integrated Services Digital Network (ISDN) DSL

Be aware of the following WAN connection details:

• When ordering a WAN service:
  • The network engineer specifies how fast the circuit should run, such as 1.544 Mbps (T1) or 56 Kbps (POTS or DS0).
  • The Telco installs the circuit running at the specified speed.
  • The network engineer purchases a CSU/DSU to connect to the end of the circuit, and then connects the router to the CSU/DSU.
  • The CSU/DSU clock rate must then be configured to match the circuit speed. Because the router is the DTE, the clock rate is received by the CSU/DSU and does not require configuration.
• When connecting a back-to-back router lab configuration, one router should be chosen as the DCE and the other router as the DTE. The cable connecting the two back-to-back 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.

 

Credit: Testout 640-802 CCNA Notes