Router Ports and Connections
In a central headquarters, where network segments converge, a larger router with a greater capacity to handle large
Figure 10.3. A router usually contains multiple interface connections to join different network segments.
In this figure, you can see that the 2505 model provides for eight Ethernet 10BASE-T connections on the left side that can be used to connect either individual computers or hubs (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.
Figure 10.4. Serial connections allow you to connect a router to wide area connections while the console port allows you to configure and manage the router.
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