Upgrading and Repairing Networks

Router Ports and Connections

In a central headquarters, where network segments converge, a larger router with a greater capacity to handle large volumes of network traffic is used. A typical router found in many corporate environments, for example, is the Cisco 2505 series. This router comes in several modelsto accommodate different network interfacesand can provide for both Ethernet and Token-Ring support. The Cisco 2505 appears in Figure 10.3, from the rear, so that you can see the physical connections.

In this figure, you can see that the 2505 model provides for eight UTP Ethernet connections on the left side that can be used to connect either individual computers or switches (using crossover cables that swap the transmit and receive wires).

Other local area network interfaces you will find on other models in this series of routers include Token-Ring connectors (usually a DB-9 connector) and Attachment Unit Interface (AUI, usually a DB-15 connector) used to connect an Ethernet transceiver to the router.

Near the middle of Figure 10.3 are two 60-pin serial connections (DB-60 connectors) that can be used to connect to wide area networks. These connections usually are made to either a modem or a CSU/DSU that interfaces with the high-speed link. Like LAN ports, different models allow for other kinds of WAN connections. For example, the 2500 series includes support for Basic Rate ISDN to connect your office to a WAN.

In Figure 10.4, you can see a close-up of the serial ports, along with two RJ-45 ports.

Next to the WAN serial connections are two RJ-45 ports labeled CONSOLE and AUX. The console port is used to connect a terminal to the router for configuration and management purposes. The terminal you use can be either a dumb terminal (such as a VT-series terminal) or a terminal emulation program running on a PC. Either way, you'll probably also have to obtain an adapter to convert the RJ-45 connector to the type of serial port used on your terminal or PC serial port. Standard serial port converters might or might not be included with the router, so be sure to check the accessories list.

The AUX port can be used to connect a modem to the router. This can be handy for dial-on-demand routing, for infrequent connections to remote sites that don't need a full-time dedicated connection.

The Cisco 2505 router is designed to handle a variety of connections and network types. However, if your network is strictly TCP/IP and uses UTP Ethernet cable, you won't need the DB-60, AUI, or other types of connections supported by the 2505. Other types of Cisco routers use RJ-45 ports or USB ports to connect to newer types of networks.