| 1.2 |  | Routers |
| 1.2.7 |  | Connecting WAN interfaces |

| WAN connections may take any number of forms. A WAN makes data connections across a broad geographic area using many different types of technology. These WAN services are usually leased from service providers. Among these WAN connection types are leased line, circuit-switched, and packet-switched. For each type of WAN service, the customer premises equipment (CPE), often a router, is the data terminal equipment (DTE). This is connected to the service provider using a data circuit-terminating equipment (DCE) device, commonly a modem or channel service unit/data service unit (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. Selecting the proper serial cable is as easy as knowing the answers to four questions: 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. This makes the selection of the serial cable connecting the network system to the serial devices a critical part in setting up a WAN. Is the network system being 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. What 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.
| Lab Activity Lab Exercise: Connecting WAN Interfaces This lab is to identify the serial interfaces on the router and identify and locate the proper cables to interconnect the routers.
| Interactive Media Activity Drag and Drop: Connecting WAN Interfaces When the student has completed this activity, the student will be able to identify the correct components and order for connecting two routers connected via WAN serial interfaces.
| Web Links Installing a Network Module http://www.cisco.com/en/US/products/ hw/routers/ps259/products_installation_ guide_ chapter09186a008007dffa.html