Connecting WAN interfaces

Connecting WAN interfaces
1.2.7 This page discusses the different forms of WAN connections.


A WAN uses many different technologies to make data connections across a broad geographic area. WAN communication services are usually leased from service providers. WAN connection types include leased line, circuit-switched, and packet-switched.

For each type of WAN service, the customer premises equipment (CPE), which is often a router, is the DTE. This is connected to the service provider through a DCE device, which is commonly a modem or CSU/DSU. This device is used to convert the data from the DTE into a form acceptable to the WAN service provider.

Perhaps the most commonly used router interfaces for WAN services are serial interfaces. Answer the following questions to select the proper serial cable:

• What is the type of connection to the Cisco device? Cisco routers may use different connectors for the serial interfaces. The interface on the left is a Smart Serial interface. The interface on the right is a DB-60 connection. It is important to select the correct serial cable to connect the network system to the serial devices. This is a critical part in setting up a WAN.

• Is the network system connected to a DTE or DCE device? DTE and DCE are the two types of serial interfaces that devices use to communicate. The key difference between these two is that the DCE device provides the clock signal for the communications on the bus. The device documentation should specify whether it is DTE or DCE.

• Which signaling standard does the device require? For each different device, a different serial standard could be used. Each standard defines the signals on the cable and specifies the connector at the end of the cable. Device documentation should always be consulted for the signaling standard.

• Is a male or female connector required on the cable? If the connector has visible projecting pins, it is male. If the connector has sockets for projecting pins, it is female.

This page concludes Module 1. The next page will provide a summary of the main points from this module.