Networking With Vista P2

The switch then forwards data from one network node to another. On basicswitches such as the type used in homes or small offices, the switch usuallyreads the MAC address of the destination node in each ethernet frame andsends the frame directly to that device. Most switches maintain a switchingtable, a record of the MAC addresses and network port numbers used by eachdevice on the network.
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Networking With Vista P2 CHAPTER 1 Understanding Ethernet Networking 23 network segment, a collection of network devices connected to a single switch. (If this network segment comprises your entire network, you can call it a switched network.) 1 Switch Computer Computer ComputerFIGURE 1.9You can use a switch as the central connection point for your network. The switch then forwards data from one network node to another. On basic switches such as the type used in homes or small offices, the switch usually reads the MAC address of the destination node in each ethernet frame and sends the frame directly to that device. Most switches maintain a switching table, a record of the MAC addresses and network port numbers used by each device on the network. As you use your network, the switch makes note of each new MAC address and adds it to the switching table, which improves overall switch performance. You can also use a switch to send data across multiple network segments. For example, you might have a network segment in one room or office and a sec- ond segment in the room or office next door. Similarly, if your network out- grows your original switch, you might add a second switch to the network instead of upgrading to a switch with more ports. To join the two segments, you have three choices: ■ Many older switches come with a special uplink port that’s designed to connect two switches by running a network cable from the uplink port of one switch to the uplink port of note The network config- uration shown in Fig- the other switch. On some of these ure 1.9—that is, multiple network nodes joined to a central connec- switches, a button controls whether tion point—is called the star the port is used as a regular RJ-45 topology. port or an uplink port. 24 Networking with Microsoft® Windows Vista™ ■ Use an ethernet crossover cable to link two switches by running the cable from any port in the first switch to any port in the second switch.1 ■ Get switches where the ports support Auto Crossover (also called Auto MDI/MDI-X crossover detection; MDI stands for Medium-Dependent Interface). This enables you to connect two switches without using an uplink port or a crossover cable. As with NICs and cables, all switches support one or more of the ethernet standards. For example, a Fast Ethernet switch will almost always support 10/100 connections, whereas a Gigabit Ethernet switch will usually support 10/100/1000 connections. Make sure you match your switch to the ethernet standard you’re using on your network. Understanding Routers You saw in the previous section that a switch forwards ethernet packets according to the device MAC address in the frame header. This works extremely well, and most modern switches are high-performance devices. However, the inherent limitation of a switch becomes obvious when you want to add an Internet connection to your network: ■ When you want to request data from a web server, it’s impossible to know the MAC address of the remote server computer, so the switch has no way to forward the data request. ■ When a web server wants to send data to your computer, it’s impossi- ble for the remote machine to know your computer’s MAC address, so the switch cannot get the data to your computer. In other words, the MAC address-based forwarding performed by a switch is limited to LAN traffic and cannot be used to handle WAN (wide area network) data. To solve this problem, you need to add a router to your network (see Figure 1.10). A router is a device that makes decisions about where to send the net- work packets it receives. So far, this soun ...