9.3 Troubleshooting Network Problems
Computer networks are moody. When they're working at their best, they're pure pleasure , seamlessly connecting PCs to one another and to the Internet. On the flip side, they break down for no apparent reason, and they act ornery just when you need them most.
This section offers tips for dealing with your network's temperamental side, helping you alleviate common frustrations and take action when things go awry.
9.3.1 Moving Your Laptop from One Network to Another
If you use a laptop at the office and at home, and you have different network setups for each, you can hit networking hell when you move from one to the other. Specifically, your settings may not work in both places, forcing you to constantly change them. Here's a quick fix: set up two IP configurations , and let Windows XP switch between the two as needed. (The IP configuration simply tells your computer whether to use the same IP address every session or to change it each time; see Sidebar 6-3 for more on IP addressing.)
If you access the Internet, you already have one IP configuration. To find it, right-click Network Places on the Start menu or desktop and choose Properties; the Network Connections folder opens. Right-click your main network connection and choose Properties. In the dialog box that opens, select the Networking tab and highlight Internet Protocol (TCP/IP), then click Properties. The Internet Protocol (TCP/IP) dialog box appears, which contains all your IP information.
To create a configuration for a second network, click "Alternate configuration"; the Alternate Configuration dialog box, shown in Figure 9-11 appears. You have two choices here:
If you use an IP address that never changes for your network, choose the User configured button, then fill in that static IP address. For the other settings in this section, check with your network administrator, or your ISP; they can tell you what settings you need to enter.
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Figure 9-10. If you frequently have top-secret chats with other people on your network, WinChat is a good choice because it's secure.
When you're done, click OK until all the dialog boxes have closed. You can now connect to either network automatically, without having to change any settings. You don't have to manually switch between the two settings, either ‚ XP does that automatically when you connect.
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Figure 9-11. Set up a second IP configuration if you have a laptop and use different IP configurations on different networks. If you only connect to networks that assign you IP addresses automatically, you most likely don't need to use a second IP configuration.
9.3.2 Finding Your Network Information
These days, knowing the network configuration information for your PC is almost as important as knowing your own address and phone number. Your network configuration information includes your IP address, host name , and MAC address ‚ thus informing a network who and where you are.
Mostly, you need to know these numbers when contacting technical support or doing your own troubleshooting, but they can also be relevant for specific tasks like sharing files with someone else via an instant messaging program. Here are a few of the numbers you should keep handy:
Your IP address . The numeric address that identifies every computer on the Internet. It's a series of numbers, such as 220.127.116.11, and whenever you do things like browse the Internet, other computers use it to locate you and send along information. You can find it manually by typing ip config /all at a command prompt. (To get to the command prompt, choose Start Run, then type in cmd and press Enter.)
Your MAC address . A MAC address is a unique number that identifies a piece of hardware, such as a router or the network card in a computer. (MAC has nothing to do with Apple computers; it stands for Media Access Control ‚ obviously.) If you use your laptop on more than one network, the system administrators at any given place may need your MAC address to get you on their network. Here's how to find it.
Choose Start Run and type in cmd , then press Enter to open the command prompt window. At the prompt, type ipconfig/all , and then press Enter. The system shows you a screen full of connection numbers; the one you're looking for is the Physical Address, under the heading Ethernet adapter Wireless Network Connection. It's 12 characters , like this: 00-D0-B7-BD-40-F1.
Your host name . The name of your computer in English; it's the name you assigned it when you set up XP.
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Release and Renew Your IP Address
One of the most common problems with network and Internet connections is a glitch with an IP address. An IP address may "time out" and no longer be valid, for example. Or, for some reason, two computers may somehow be given the same IP address, causing a spate of conflicts.
Fortunately, Wnticfg.exe ‚ an excellent utility from Microsoft, despite its name ‚ can help solve these problems. Download it for free from Microsoft at http://www.microsoft.com/windows2000/techinfo/reskit/tools/existing/wntipcfg-o.asp. (Previous versions of Windows had a built-in utility called Winipcfg.exe that provided essentially the same information Wnticfg.exe offers. As of XP, Winipcfg is history.)
Once you install it, look in My Computer C: Program Files Resource Kit for Wnticfg.exe and open the program. It runs as a compact little screen, but if you want to see expanded information about your PC's network configuration, click More Info .
To fix an IP problem, try this. Click Release (at the bottom of the window) to clear your IP address, and then click Renew to get a new one. Taking this simple step often solves many stubborn connectivity problems.
9.3.3 The Network Diagnostics Tool
If you're experiencing a network or Internet connection problem, Windows XP's built-in diagnostics tool may be able to reveal the culprit. With just a few mouse clicks, it tests basic settings, a variety of network protocols, and whether your hardware is functioning properly.
To use the diagnostics tool, choose Start "Help and Support" "Networking and the Web" "Fixing Networking or Web Problems" "Diagnose network configuration and run automated networking tasks."
The next screen that appears offers two choices: "Scan your system" or "Set scanning options." The first option scans your system immediately for problems, while the second choice lets you customize what it scans ‚ this is the option you want. Under Options, make sure you turn on Domain Name System (DNS), Dynamic Host Configuration Protocol (DHCP), default gateways, IP address, and Windows Internet Naming Service (WINS).
When you click "Scan your system," XP performs its magic. After several minutes, a report like the one pictured in Figure 9-12 appears, letting you know if anything is wrong.
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Figure 9-12. This report can help you fix the problem yourself, or you can pass along the details to tech support. If you click Save to File, XP saves the report as an HTML file. To view past reports , click Show Saved Files.
9.3.4 Repairing a Broken Network Connection
Network connections break more often than highway repair crews. TCP/IP problems are among the most common network problems, and have to do with the underlying communications rules that control the Internet. (TCP/IP stands for Transmission Protocol/Internet Protocol and is the standard for transmitting data over networks.)
Here's how to deal with TCP/IP attitude:
Release and renew your IP address . Release the connection by going to the command prompt (choose Start Run, then type in cmd and press Enter.), and then typing the command ipconfig /release [adapter name]. [Adapter name] is the name of the device whose connection is broken, for example, Broadcom Controller). Then renew the connection by using the command ipconfig /renew [adapter name] . You can also release and renew an IP address using the Wntipcfg utility, as detailed in Sidebar 9-3.
Try automated repair . In the Network Connections folder, right-click the broken connection and choose Repair. (To access the Network Connections Folder, right-click My Network Places and choose Properties.) Frequently, XP can solve the problem for you by itself.
Run the Network Setup Wizard . This walks you through TCP/IP and network configuration, helping you to correct any errors you may have inadvertently introduced. To run it, choose Start Control Panel Network and Internet Connections, and then click Network Connections. Under Common Tasks, click Network Setup Wizard.
Reset your router . If you have a home network, the problem may lie with your router, or in the connection between the router and your broadband provider. Follow the directions in your router's documentation to reset it.
Note: If you have a router at home, and you use a Virtual Private Network (VPN), or encrypted connection, to reach your corporate network from your bedroom office, one particular router setting can kill off the connection. Check your router settings (Section 9.2.7) for something like "Block WAN Request," which can disable VPN access.This setting usually comes turned on, and it stops certain kinds of Internet traffic from getting through to your home network. It also blocks access to many VPNs. You can usually change this setting by logging into your administrator's account and turning off any setting that prevents WAN requests .
Reset your cable modem or DSL modem . If you have a broadband connection, there may be a problem with the assignment of your IP address by your ISP. Turn off your cable or DSL modem (it might have just a plug but no on/off button), unplug its Ethernet cable, and leave it off for five minutes. Now restart it. You can also try releasing and renewing your IP address (Sidebar 9-3) after you turn the connection back on, or resetting your router at the same time you reset your broadband modem.
Reset TCP/IP to its original configuration . If all else fails, try to reset your TCP/IP configuration to the same state it was in when XP was first installed on the computer. To do that, use the NetShell utility by going to the command prompt and entering this command: netsh int ip reset . Now press Enter.