Ccna routing and Switching Complete Study Guide

CSU/DSU

CSU/DSU

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Chapter 21 

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  Wide Area Networks

The idea behind a WAN is to be able to connect two DTE networks through a DCE 

network. The DCE network includes the CSU/DSU, through the provider’s wiring and 

switches, all the way to the CSU/DSU at the other end. The network’s DCE device  

(CSU/DSU) provides clocking to the DTE-connected interface (the router’s serial interface).

As mentioned, the DCE network provides clocking to the router; this is the CSU/DSU. 

If you have a nonproduction network and you’re using a WAN crossover type of cable and 

do not have a CSU/DSU, then you need to provide clocking on the DCE end of the cable by 

using the 

clock rate

 command. To find out which interface needs the 

clock rate

 com-

mand, use the 

show controllers 

int

 command:

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