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that are given temporarily to machines. DHCP is especially handy for networks of a lot of laptops that join and leave the network on a regular basis. Why give a machine that is on the network for only a few hours a day a static IP address? For that reason, DHCP is quite popular. If you add a NIC to a Windows system, the default TCP/IP settings are set to use DHCP. When you accept those automatic settings, you’re really telling the machine to use DHCP (Figure 23-32).

Figure 23-30 Setting up WINS to use DHCP

Figure 23-31 Setting a static IP address

Figure 23-32 Automatically obtain an

TCP/IP Tools

All versions of Windows come with handy tools to test TCP/IP. Those you’re most likely to use in the field are PING, IPCONFIG, NSLOOKUP, and TRACERT. All of these programs are command prompt utilities. Open a command prompt to run them; if you just place these commands in the Run command, you’ll see the command prompt window open for a moment and then quickly close!

PING You’ve already seen PING, a really great way to see if you can talk to another system. Here’s how it works. Get to a command prompt and type ping followed by an IP address or by a DNS name, such as ping www.chivalry.com. Press the ENTER key on your keyboard and away it goes! Figure 23-33 shows the common syntax for PING.

PING has a few options beyond the basics that CompTIA wants you to know about. The first option is –t. By using the –t switch, PING continuously sends PING packets until you stop it with the break command (CTRL-C). The second option is the –l switch that enables you to specify how big a PING packet to send. This helps in diagnosing specific problems with the routers between your computer and the computer you PING.

IPCONFIG Windows offers the command-line tool IPCONFIG for a quick glance at your network settings. Click Start | Run and type CMD to get a command prompt. From the prompt, type IPCONFIG /ALL to see all of your TCP/IP settings (Figure 23-34).

When you have a static IP address, IPCONFIG does little beyond reporting your current IP settings, including your IP address, subnet mask, default gateway, DNS servers, and WINS servers. When using DHCP, however, IPCONFIG is also the primary tool for releasing and renewing your IP address. Just type ipconfig/renew to get a new IP address or ipconfig /release to give up the IP address you currently have.

Figure 23-33 PING syntax

Figure 23-34 IPCONFIG /ALL on Windows Vista

NSLOOKUP NSLOOKUP is a powerful command-line program that enables you to determine exactly what information the DNS server is giving you about a specific host name. Every version of Windows makes NSLOOKUP available when you install TCP/IP. To run the program, type NSLOOKUP from the command line and press the ENTER key (Figure 23-35). Note that this gives you a little information but the prompt has changed? That’s because you’re running the application. Type exit and press the ENTER key to return to the command prompt.

Figure 23-35 NSLOOKUP in action

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NOTE You can do some cool stuff with NSLOOKUP, and consequently some techs absolutely love the tool. It’s way outside the scope of CompTIA A+ certification, but if you want to play with it, type HELP at the NSLOOKUP prompt and press ENTER to see a list of common commands and syntax.

TRACERT The TRACERT utility shows the route that a packet takes to get to its destination. From a command line, type TRACERT followed by a space and an IP address. The output describes the route from your machine to the destination machine, including all devices the packet passes through and how long each hop takes (Figure 23-36).

Figure 23-36 TRACERT in action

TRACERT can come in handy when you have to troubleshoot bottlenecks. When users complain of difficulty reaching a particular destination by using TCP/IP, you can run this utility to determine whether the problem exists on a machine or connection over which you have control, or if it is a problem on another machine or router. Similarly, if a destination is completely unreachable, TRACERT can again