Chapter 4. Working with Cisco Equipment

Chapter 4. Working with Cisco Equipment

Products

The CCNA exam does not test you about product-specific knowledge. That is to say, you are not expected to know what feature cards are available for a 6500 series switch, but you do need to understand the differences between a router and a switch, and you need to understand how their configuration requirements vary. For our purposes, we use a Catalyst 2960 or 3560 switch and a 1600, 1700, or 2600 series router as example devices. Most of the commands you learn in this chapter also apply to more advanced models.





External Connections

Cisco devices make connections to other devices, and collectively they all create a network. At some point, making a connection means plugging in a cable—even with a wireless system. This section examines some of the various connections found on Cisco routers and switches.

Console

When you first obtain a new Cisco device, it won't be configured. That is to say, it will not do any of the
customized functions you might need; it does not have any IP addresses, and it is generally not going to do what you paid for. However, if you buy a 2960 switch, turn on the power, and plug PCs in to it, it will work to connect those PCs with no further configuration, but you are missing out on all the cool stuff and advanced features. Your new router, on the other hand, will not be capable of doing much for you at all, even if you plug devices into the interfaces. Routers need basic configuration to function on a network, or they simply consume power and blink at you.

The console port is used for local management connections. This means that you must be able to physically reach the console port with a cable that is typically about six feet long. The console port looks exactly like an Ethernet port. It uses the same connector, but it has different wiring and is often (but not always) identified with a pale blue label that says "CONSOLE." If the device is not configured at all—meaning, if it is new or has had a previous configuration erased—the console port is the only way to connect to it and apply configurations.



Serial Port

A Cisco serial port is a proprietary design, a 60-pin D-sub. This connector can be configured for almost any kind of serial communication. You need a cable that has the Cisco connector on one end and the appropriate type of connector for the service you want to connect to on the other.

Serial ports are almost always used for WAN connections and use one of several Layer 2 protocols including Frame Relay, PPP, and HDLC. Serial ports can also connect to an ISDN Primary Rate Interface (PRI) service or regular analog telephone service. (For a telephone service, you need a special hardware type called an asynchronous serial port and a modem.)

HDLC is the default encapsulation on a Cisco serial port, and the HDLC protocol here is a Cisco proprietary version of the standardized ISO HDLC that can run multiple Layer 3 protocols, which the ISO version can't do.
You might have one or more serial ports depending on what you need and what you buy.


Exam Alert

You will need to know the three WAN encapsulations for a serial port: HDLC, PPP, and Frame Relay. These will be discussed in more detail later.

Know that Cisco's HDLC is the default encapsulation for serial ports.

Other Connections

Your router may use a T1 controller card to connect to a T1 WAN service. The controller will probably have a label that reads "T1 CSU/DSU," with a plug that looks like the RJ-45 connector but is actually an RJ-48. You can also buy ports for High-Speed Serial communication (perhaps ATM) or even different fiber-optic connections. What you purchase will depend on the services you need to connect to, the model of router you buy, and of course how much money you want to spend. Although the "Other Connections" listed here are by no means an exhaustive list of your options, they are the most commonly used. These connection types are not tested, but are included here for your interest.

Reference : CCNA Exam Cram (Exam 640-802), Third Edition by Michael Valentine; Andrew Whitaker