In this chapter
Browsing the Internet is great fun—and very useful, too. In fact, watch as I instantly transfer millions of dollars from my secret Swiss bank account to… Wait a minute, what's a 404 Server Not Found Error? What's going on? Did the modem disconnect? Is the IRS closing in on me? Help! Where's my money?!
If you've used the Internet for any length of time, this scene may seem all too familiar—except for the bit about the Swiss bank account (a guy can dream, can't he?). Connecting to the Internet and using the Web is an amazingly user-friendly experience, yet we can't escape the basic fact that it's a staggeringly complex system. If something goes wrong at any step along the way between your fingertips and a server somewhere off in cyberspace, the whole system comes to a crashing halt. Where do you begin to find and fix the problem?
In this chapter, I'll show you the basic strategies to use when tracking down Internet problems, and then I'll briefly discuss some of the diagnostic tools available to help you pinpoint the trouble.
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Experiment with the diagnostic tools when your network and Internet connection are operating correctly to learn how the programs work and what sort of output you should expect. This way, as we'll discuss in the next section, if you run into trouble later, you can compare the results to what you saw when things were working.
The best tool to have on hand when you're diagnosing Internet problems is information about what you should expect when your connection is working.
It's very helpful to collect correct output of the TCP/IP diagnostic programs, which I'll discuss later in this chapter, and store the copies in a notebook for reference purposes. You can use the PrntScrn key to take snapshots of the output and setup windows, and then paste the pictures into a WordPad document as a super-fast way of recording this stuff.
Here are some things to record:
The output of
tracertto a sample Web site.Tracertis a tool that records all the intermediate steps that Internet data takes getting from your computer to a site out on the Net. Knowing what the route looks like when things are working can help you tell whether a problem is in your computer or out somewhere on the Internet, beyond your control.The output of
ipconfig /allon each of your computers, while you're connected to the Internet. Ipconfig lists all of your networking settings so you can check for mistakes.The network hardware and protocol configuration dialog boxes in Network Connections, as pictures snapped with PrntScrn. If you have a network or a network adapter that you use for a broadband cable or DSL Internet connection, it's handy to record the setup information in case you need to reenter it at a later date. You might need to do that if you replace your network adapter, for example.
The configuration of any routers or network connection equipment. If you have an Internet connection sharing device, it's a good idea to record its correct settings in case they are accidentally changed, or if you update or replace the device. You can do this by printing each of its setup screens from your Web browser.
The settings for any dial-up connections used. Many ISPs talk you through their setup, and it's important to record the setup information in case you need to reconstruct it someday.
Diagrams showing network cabling, hubs, routers, and computers. If your three-year-old is a budding network installer and rewires your computer, it's handy to have a diagram of the correct setup to help you get the all the wiring spaghetti back in order.
In a business setting, documentation of your LAN configuration is a “due diligence” issue—it's not optional. Keep it up-to-date, and if you use an outside contractor for network installation or management, be sure that your contract requires good documentation.
This way, you'll be armed with supportive information if a problem does occur.
A functioning Internet connection depends on a whole chain of correctly functioning hardware and software components that reach all the way from your keyboard to a computer that may be halfway around the world. Troubleshooting is a real detective's art, and it's based more on methodical tracking down of potential suspect problems than intuition. If something goes wrong, what you have to do is go through each component in turn, asking “Is this the one that's causing the problem?”
Let's assume that you are having trouble using a certain Web site. It could be that…
You can view some of its pages, but not others; or, you see text displayed, but, say, not the streaming video or sound.
In this case, you know that your Internet connection itself is fine, as evidenced by the fact that text and some pages do appear. The problem is that the video or sound application isn't working. To proceed to fix this problem, check the appropriate chapter in this book, or see if the Web site itself has any online help.
Nothing on this particular site is responding. In this case, see if you can view any other Web site, for example, www.google.com or www.quepublishing.com; use your imagination.
If you get a response from even one Web site, again, your Internet connection is fine. The problem is most likely with the site you're trying to use, or with your ISP. Check to be sure that Internet Explorer isn't set up to block access to the site you're interested in (See Chapter 9, “Browing the World Wide Web from Internet Explorer,” for more help on this topic).
You can't view any Web pages on any site at all. If you poke around and find that you can't view any Web site at all, then you know that your Internet connection itself is at fault. This chapter will help you find out what's wrong.
To that end, Figures 14.1 and 14.2 show flowcharts to help direct you to source of the problem. The first chart is for dial-up connections to an ISP, and the second is for LAN connections. If you're having Internet connection trouble, follow the appropriate flowchart. The endpoints in each flowchart suggest places to look for trouble. I'll discuss these in the sections that follow.
Software configuration problems can easily be the cause of Internet connection problems, and it's fairly easy to determine that this is the problem—you can't make any Internet connection whatsoever, although the Device Manager says your network card or modem seems to be working correctly. The potential problems depend on the type of Internet connection you use.
If your modem appears to connect to your ISP but, even though connected, you still can't access any Web pages or Internet services, here are some steps you can take:
In Internet Explorer, select Tools, Internet Options. Select the Connections tab. Be sure you have selected the correct dial-up connection. Click LAN Options and be sure that Use a Proxy Server is not checked, as shown in Figure 14.3.
Click Start, Connect To, and right-click your Dial-Up connection. Select Properties, and view the Networking tab. The type of dial-up server should be PPP, and under Components Used By This Connection, only Internet Protocol and QoS Packet Scheduler should be checked, as shown in Figure 14.4.
On the Security tab of your connection's Properties sheet (refer to step 2), be sure that Validate My Identity is set to Allow Unsecured Password for an ISP, or Require Secured Password if you're connecting to your office LAN.
If none of these steps identifies a problem, it's time to call your ISP for assistance. You might have to spend a half hour listening to really bad music on hold, but at this point, it's their job to help you get online and they should help you cheerfully and expertly (otherwise, you should get a new ISP).
If your computer connects to a cable or DSL modem, you may have one or two network cards installed in your computer, depending on whether you're sharing the high-speed connection on your LAN.
Here's how to check for the proper settings:
In a command prompt window, type
ipconfig /all. Be sure that your IP address and DNS information for the network card that connects to your high-speed modem is accurate. Your ISP's tech support people can help you confirm this.If your DSL provider requires you to “sign on” before using the Internet, you'll be using a sort of “dial-up” connection, except that the connection is made digitally over the DSL network. You will have set up a connection using Connect Using a Broadband Connection That Requires a User Name and Password as described in Chapter 8.
If this is the case, and if you use a LAN adapter to connect to your DSL modem, this LAN adapter will have an IP address that is used only to communicate with your DSL modem. Be sure to check with your ISP to be certain that this computer-to-modem connection is configured correctly; if it's not, you won't be able to make the connection to your ISP.
Then, be sure to use the Connection icon to connect to your ISP. You can get to it quickly using Start, Connect To.
When the logon process has completed, ipconfig should show a dial-up connection with a different IP address. This is your real, public Internet address for the duration of the call.
If you're sharing a high-speed connection to a LAN using two network cards in your computer, be sure that you've enabled sharing on the correct connection! The connection to check as “shared” is the one that connects to your high-speed DSL or cable modem. The LAN-side connection is not the shared connection and should have an IP address of
192.168.0.1. Internet Connection Sharing is described in Chapter 19, “Connecting Your LAN to the Internet”.
If you connectto the Internet via a wired or wireless connection on your LAN, the first question is, can you communicate with other computers on your LAN? To test this, you should use the ping command.
Open a Command Prompt window and type the command ipconfig. The output of ipconfig will list a number called a gateway address. Test the gateway address with the ping command, for example
ping 192.168.0.1
This tests the connection to the computer or router that is sharing its Internet connection. If ping says “Request timed out” rather than listing four successful replies, you have a LAN problem that you'll need to fix first. If you are using a wireless network connection, be sure that your wireless connection is working correctly, that you are connected to the correct wireless network, and have the correct network key entered. Chapter 22 is devoted to LAN troubleshooting.
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Windows has a “repair” function that resets all of the software components of a LAN connection, including the DHCP address assignment. This often solves LAN problems. To use it, open the Network Connections page, find your LAN or wireless connection, right-click it, and select Repair.
If you can communicate with other computers on the LAN but not the Internet, can anyone else on your LAN access the Internet? If no one can, the problem is in your LAN's connection to the Net. If your LAN uses Internet connection sharing, go to the sharing computer and start diagnosing the problem there. Otherwise, follow these steps:
Open a command prompt window and type
ipconfig /allto view your TCP/IP settings. The output will appear similar to that shown in Listing 14.1.Example 14.1. Output from the
ipconfig /allCommandWindows IP Configuration Host Name . . . . . . . . . . . . : ambon Primary Dns Suffix . . . . . . . : Node Type . . . . . . . . . . . . : Unknown IP Routing Enabled. . . . . . . . : No WINS Proxy Enabled. . . . . . . . : No Ethernet adapter Local Area Connection: Connection-specific DNS Suffix . : mycompany.com Description . . . . . . . . . . . : Realtek RTL8139 Family PCI Fast Ethernet NIC Physical Address. . . . . . . . . : 00-C0-CA-14-09-7F Dhcp Enabled. . . . . . . . . . . : Yes Autoconfiguration Enabled . . . . : Yes IP Address. . . . . . . . . . . . : 192.168.0.102 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.0.1 DHCP Server . . . . . . . . . . . : 192.168.0.1 DNS Servers . . . . . . . . . . . : 192.168.0.4 207.155.183.72 206.173.119.72 Lease Obtained. . . . . . . . . . : Sunday, August 19, 2001 5:57:56 PM Lease Expires . . . . . . . . . . : Monday, August 20, 2001 5:57:56 PMCheck the following:
The DNS suffix search list and/or the connection-specific DNS suffix should be set correctly for your ISP's domain name, or your company's domain name. (This is helpful, but not crucial.)
The IP address should be appropriate for your LAN. If you're using Internet Connection Sharing, the number will be
192.168.0.xxx. If you're using a hardware connection sharing device, the number may be different.If your IP address appears to be
169.254.0.xxx, the sharing computer or router was not running the connection-sharing service when you booted up your computer, or it is no longer set up to share its connection. Get the sharing computer or router restarted and then skip to step 2.The default gateway address should be the IP address of your router or sharing computer, usually something like
192.168.0.1or192.168.1.1.The default gateway address and your IP address should be identical for the first few sets of numbers, corresponding to those parts of the subnet mask that are set to 255. That is, both might start with
192.168.0or192.168.1.If your computer gets its IP address information automatically, DHCP Enabled should be set to Yes. If your computer has its IP address information entered manually, no DHCP server should be listed.
If you're using Connection Sharing, the DNS server address will be
192.168.0.1. Otherwise, the DNS server numbers should be those provided by your ISP or network administrator.If your computer gets its settings automatically or uses a shared connection, continue with the next two steps.
Be sure the master router or sharing computer is running. Then, in the Network Connections window, click your Local Area Connection icon and select Repair This Connection from the task list. This may solve the problem.
Repeat the
ipconfigcommand and see whether the correct information appears now. If it does, you're all set. If not, the master computer or the router is not supplying the information that I described above, and needs to be set correctly before you can proceed.
These steps should take care of any software configuration problems, and there isn't much more that could be causing a problem, as long as your network hardware is functioning correctly. If none of these steps indicates or solves the problem, check that your network or modem hardware is functioning correctly.
If you suspect hardware as the source of your Internet connection problems, check the following:
Log on as a Computer Administrator. On the Start menu, right-click My Computer and select Manage to open Computer Management. Select Device Manager. Look for any yellow exclamation point (!) icons in the device list; if your network adapter is marked with this trouble indicator, you'll have to solve the hardware problem before continuing. See Chapter 25, “Maintaining and Optimizing System Performance,” for hardware troubleshooting tips.
Still in Computer Management, check the Event Viewer for an informative error message that may indicate a hardware problem.
Use
ipconfigon each of your computers to check that all the computers on your LAN have the same gateway and network mask values, and similar but distinct IP addresses.If your LAN has indicator lights on the network cards and/or hubs, open a command prompt window and type
ping -tx.x.x.x, wherex.x.x.xis your network's Default Gateway address. This forces your computer to transmit data once per second. Confirm that the indicator lights blink on your LAN adapter and the hub, if you have one. This test may point out a cabling problem.If your hub or LAN card's indicator doesn't flash, you may have a bad LAN adapter, the wrong driver may be installed, or you may have configured the card incorrectly. You can stop the Ping test by pressing Ctrl+C when you're finished checking.
Modems can have a greater variety of problems than network adapters. Here are a few steps you can take to determine what the problem might be:
Before getting too frustrated, check the obvious one more time: Is a functioning telephone line connected to the right socket on the modem? Unless you're using an ISDN modem, it also doesn't hurt to plug in an extension phone and listen as the modem dials and your ISP answers. You must somehow put the extension on the “line” side of the modem, though, because most modems disable the “telephone” jack when dialing.
If dialing was actually taking place but you couldn't hear it, run the Phone and Modem Options (open the Control Panel and select Network Connections). Select the Modems tab, select Properties, and then turn up the speaker volume.
If you have a voicemail system that uses a stutter dial tone to indicate that you have messages waiting, your modem may not dial when the stutter is active. If this is the case, in this same Control Panel dialog, disable the Wait for Dial Tone Before Dialing option.
If you have an external analog or ISDN modem, be sure that it's plugged in and turned on. When you attempt to make a connection, watch for flickering in the Send Data LEDs. If you don't see flickering, your modem cable might not be installed correctly.
Check the Event Viewer for informative error messages that may indicate a hardware problem.
In the Start menu, right-click My Computer, select Manage, and select Device Manager. Look for any yellow exclamation point (!) icons in the device list; if a modem or port is marked with this trouble indicator, you'll have to solve the hardware problem before continuing. See Chapter 25 for hardware troubleshooting tips.
In the Dial-Up Connection's Properties Option tab, check Prompt for Phone Number and try to make the connection. This will show you the actual number being dialed. Verify that the call waiting code, outside line access codes, and area code are correct. These are set on the connection's General tab and in the Phone and Modem Options control panel (on the Dialing Rules dialog box, select the proper location and click Edit).
If you have an analog or ISDN modem, and dialing is taking place but no connection is made, in the Device Manager or Control Panel Phone and Modem Properties, view the modem's Properties dialog. Select the Diagnostics tab, and check Append to Log. Close the dialog, and try to make the connection again. Go back to the Properties dialog, and select View Log. This log may indicate what is happening with the modem. Be sure to uncheck Append to Log when you're finished or the file that stores this information could grow to enormous proportions.
Try reducing the Maximum Port Speed (computer-to-modem connection speed) setting in Modem Properties to 19200. If this solves your problem, you need a new modem, or, if you have an external serial modem, a higher-quality serial port card.
Modems are much more reliable these days than they were in the 1980s and 1990s. Still, compatibility problems and trouble due to poor telephone line quality still occur from time to time. If your modem fails to make a connection, or disconnects by itself, here are a few things to look for:
If the ISP's modem answers but you don't establish a connection, your modem may be incompatible; call your ISP for assistance.
If your modem disconnects and you are told that there was a problem with your username or password, try to connect again and check these entries carefully. If you try two or three times and still can't connect, contact your ISP for help. I've known them to disable accounts for various reasons, from non-payment to, well, no reason at all.
Create and view a log file of modem activity and look for error messages indicating a protocol negotiation error. Your ISP can assist with this as well.
If your modem makes screeching sounds for about 15 seconds and hangs up, your modem is probably incompatible with the equipment used at your ISP, and one of you needs to get an updated modem. Before you buy a new one, note that some modems can be updated via software. Check the manufacturer's Web site for information.
If your connection works but the modem disconnects after a certain amount of time, there are two possible causes. If your connection was sitting idle, you may have run into the Windows inactivity timer. View the dial-up connection's properties in Network Connections and select the Options tab. Check the entry Idle Time Before Hanging Up. Increase the time (or stay busier!). You might enable the modem log and see whether it provides an explanation if this recurs. Your ISP may also have set up their equipment to disconnect you after a certain period of inactivity.
If you don't think that idle time was the cause, your connection may have been interrupted by call waiting. On the connection's General tab, check Use Dialing Rules and select Rules and Edit. Verify that you've chosen to disable call waiting and have selected the proper call waiting turn off setting (for example, *70). Some newer modems are able to cope with call waiting, and even alert you to a call coming in. If you really rely on call waiting, it might be time for an upgrade. Although, in this case, you'd probably be better suited switching to a cable or DSL connection if one is available to you.
If none of these are the cause, you may simply have a scratchy telephone line or a flagging older modem. This is an annoying problem and difficult to diagnose. Try changing modems.
If your modem is making contact with your ISP, but despite a solid modem connection you still can't use the Internet, see the next section for tips on diagnosing Internet connectivity problems.
If you think you are connected to your ISP but still can't communicate, you can use some of the command-line tools provided with Windows XP to trace TCP/IP problems. (TCP/IP is the network language or protocol used by the Internet; see Chapter 15 for an introduction to networking and protocols.)
To run the command-line utilities, open a Command Prompt box with Start, More Programs, Accessories, Command Prompt. Then type in the commands as I'll describe them below. If you're not familiar with command-line utilities you can launch Windows Help (Start, Help and Support), and search for the command names, such as “ping” and “tracert.” You can also open a Command Prompt window and type the command name followed by /?, as in
Ping /?
Now, let's go through some of the Windows XP TCP/IP diagnostic and command-line utilities.
NOTE
If you're a UNIX devotee, you'll find these utilities very familiar, if not identical, to their UNIX counterparts. If you're new to TCP/IP networking or debugging, you might find these utilities a little unfriendly. (Welcome to the world of networking!)
Ipconfig is one of the most useful command-line utilities available with Windows XP, because it displays the current IP address information for each of your computer's network adapters and active dial-up connections. On networks that assign addresses automatically, ipconfig provides the only way to find out what your computer's IP address is, should you ever need to know it.
After opening a command prompt window, typing the command
ipconfig
returns the following information (of course the IP, subnet, and gateway information ipconfig provides will be different for your computer, and you might see a dial-up connection listed rather than a LAN adapter):
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . : mycompany.com
IP Address. . . . . . . . . . . . : 202.201.200.166
Subnet Mask . . . . . . . . . . . : 255.255.255.224
Default Gateway . . . . . . . . . : 202.201.200.190
If you type the command
Ipconfig /all
Windows displays additional information about your DNS settings, including
Host name | The name you gave your computer. |
Primary DNS suffix | The Internet domain to which your computer primarily belongs. (You might temporarily belong to others as well while using a dial-up connection.) This might be blank; it is not a problem. |
Node type | The method that Windows uses to locate other computers on your LAN when you use Windows Networking. This should be Hybrid if you have a Windows Server or a WINS server on your LAN; otherwise, the node type should say Broadcast. |
DNS suffix search list | Alternative domain names used if you type just part of a host name and the default domain does not provide a match. |
Connection-specific DNS suffix | The domain name for this particular connection. This is most applicable to dial-up connections. |
DHCP enabled | If set to Yes, this adapter is set to receive its IP address automatically. If set to No, the address was set manually. |
DNS servers | IP addresses of domain name servers. |
Ipconfig displays most of the information in the Network and Dial-Up Connection Properties dialog box, but it shows their real-world values. This makes it an invaluable “first stop” when troubleshooting any network problem. If you determine that an Internet connection problem lies in your equipment somewhere (because you cannot access any Internet destinations), typing ipconfig /all will tell you whether your network setup is correct. You'll want this information at hand before calling your ISP for assistance.
If you try to browse the Internet or share files with other computers on your LAN and get no response, it could be because the other computer isn't getting your data or isn't responding. After ipconfig, ping is the most useful tool to determine where your Internet connection or your network has stopped working.
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You can type ping x.x.x.x, replacing x.x.x.x with the default gateway address or the address of any other operational computer on the Internet or on your network, if you have one, and in an instant know whether your dial-up or high-speed modem, computer, network hardware, and cabling are operating properly. If echoes come back, the physical part of your network is functioning properly. If they don't, you can use tracert and other tools explained later in this chapter to see why.
Here's how it works:
The
pingcommand sends a few packets of data to any computer you specify.The other computer should immediately send these packets right back to you.
Then, ping lets you know whether the packets come back.
Therefore, ping tests the low-level communication between two computers. If ping works, you know that your network wiring, TCP/IP software, and any routers in between you and the other computer are working. Ping takes several options that can customize the type and amount of output it reports back to you. There are three especially useful variations of these options, the first two of which are
C:> ping hostname
and
C:> ping nnn.nnn.nnn.nnn
These variations transmit four packets to the host or IP address you specify and tell you whether they return. This command returns the following information:
C:> ping www.mycompany.com Pinging sumatra.mycompany.com [202.222.132.163] with 32 bytes of data: Reply from 202.222.132.163: bytes=32 time<10ms TTL=32 Reply from 202.222.132.163: bytes=32 time<10ms TTL=32 Reply from 202.222.132.163: bytes=32 time<10ms TTL=32 Reply from 202.222.132.163: bytes=32 time<10ms TTL=32
In this example, the fact that the packets returned tells us that the computer can communicate with www.mycompany.com. It also tells us that everything in between is working as well.
NOTE
It's not uncommon for one packet of the four to be lost; when the Internet gets congested, sometimes ping packets are discarded as unimportant. If any come back, the intervening networks are working.
Another useful variation is to add the -t option. This makes ping run endlessly, once per second, until you press Ctrl+C. This is especially helpful if you're looking at indicator lights on your network hub, changing cables, and so on. The endless testing lets you just watch the screen to see whether any changes you make cause a difference.
Ping is a great quick test of connectivity to any location. If the ping test fails, use tracert or pathping to tell you where the problem is. Ping is a good quick tool to use to discover whether an Internet site is alive. (However, some large companies have made their servers not respond to ping tests at all. ping www.microsoft.com doesn't work, ever, even with a good Internet connection. Guess Microsoft got tired of being the first site everyone thought of to test their Internet connections.)
Tracert is similar to ping: It sends packets to a remote host and sees whether packets return. However, tracert adds a wrinkle: It checks the connectivity to each individual router in the path between you and the remote host. (Routers are the devices that connect one network to another. The Internet itself is the conglomeration of a few million networks all connected by routers). If your computer and Internet connection are working but you still can't reach some or all Internet sites, tracert can help you find out where the blockage is.
In tracert's output, the address it tests first is your local network's gateway (if you connect to the Internet via a high-speed connection or a LAN) or the modem-answering equipment at your ISP's office (if you're using a dial-up connection). If this first address responds, you know your modem, LAN, or broadband connection is working. If the connection stops after two or three routers, the problem is in your ISP's network. If the problem occurs farther out, there may be an Internet outage somewhere else in the country.
Here's an example that shows the route between my network and the fictitious Web server www.fictitious.net. Typing
C:> tracert www.fictitious.net
returns the following:
Tracing route to www.fictitious.com [204.179.107.3] over a maximum of 30 hops: 1 <10 ms <10 ms <10 ms 190.mycompany.com [202.201.200.190] 2 <10 ms <10 ms 10 ms 129.mycompany.com [202.201.200.129] 3 20 ms 20 ms 20 ms w001.z216112073.sjc-ca.dsl.cnc.net [216.112.73.1] 4 10 ms 10 ms 10 ms 206.83.66.153 5 10 ms 10 ms 10 ms rt001f0801.sjc-ca.concentric.net [206.83.90.161] 6 10 ms 20 ms 20 ms us-ca-sjc-core2-f5-0.rtr.concentric.net [205.158.11.133] 7 10 ms 20 ms 10 ms us-ca-sjc-core1-g4-0-0.rtr.concentric.net [205.158.10.2] 8 10 ms 20 ms 20 ms us-ca-pa-core1-a9-0d1.rtr.concentric.net [205.158.11.14] 9 10 ms 20 ms 20 ms ATM2-0-0.br2.pao1.ALTER.NET [137.39.23.189] 10 10 ms 20 ms 20 ms 125.ATM3-0.XR1.PAO1.ALTER.NET [152.63.49.170] 11 10 ms 10 ms 20 ms 289.at-1-0-0.XR3.SCL1.ALTER.NET [152.63.49.98] 12 20 ms 20 ms 20 ms 295.ATM8-0-0.GW2.SCL1.ALTER.NET [152.63.48.113] 13 20 ms 20 ms 20 ms 2250-gw.customer.ALTER.NET [157.130.193.14] 14 41 ms 30 ms 20 ms www.fictitious.com [204.179.107.3] Trace complete.
You can see that between my computer and this Web server, data passes through 13 intermediate routers, owned by two ISPs.
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When your Internet connection is working, run tracert to trace the path between your computer and a few Internet hosts. Print and save the listings. Someday when you're having Internet problems, you can use these listings as a baseline reference. It's very helpful to know whether packets are stopping in your LAN, in your ISP's network, or beyond when you pick up the phone to yell about it.
I should point out a couple of tracert's oddities. First, notice in the example that on the command line I typed www.fictitious.net, but tracert printed www.fictitious.com. That's not unusual. Web servers sometimes have alternative names. Tracert starts with a reverse name lookup to find the canonical (primary) name for a given IP address.
There's another glitch you might run into. For security reasons, many organizations use firewall software or devices, which block tracert packets at the firewall between their LAN and the Internet. In these instances, tracert will never reach its intended destination even when regular communications are working correctly. Instead, you'll see an endless list that looks like this:
14 * * * Request timed out. 15 * * * Request timed out. 16 * * * Request timed out.
This continues up to tracert's limit of 30 probes. Just press Ctrl+C to cancel the test if this happens. If tracert was able to reach routers outside your own LAN or PC, your equipment and Internet connection are fine and that's all you can hope for.
Pathping is relatively new to Windows's toolkit, having first appeared in Windows 2000. It provides the function of tracert and adds a more intensive network traffic test.
Pathping performs the route-tracing function faster than tracert because it sends only one test packet per hop, compared to tracert's three.
Then, after determining the route, pathping does a punishing test of network traffic at each router by sending 100 ping packets to each router in the path between you and the host you're testing. It measures the number of lost packets and the average round trip time for each hop, and it displays the results in a table.
The results tell you which routers along the way are experiencing congestion, because they will not be able to return every echo packet they're sent, and they may take some time to do it. Performing the pathping test can take quite a while. Fortunately, you can cancel the test by pressing Ctrl+C, or you can specify command-line options to shorten the test. A reasonably quick test of the path to a site, say www.quepublishing.com, can be performed using just 10 queries instead of the default 100, using this command:
pathping -q 10 www.quepublishing.com
You can type
pathping /?
Most of us have at most one modem or one LAN adapter through which we make our Internet and other network connections, but Windows Networking components are sophisticated enough to handle multiple LAN and dial-up adapters in one computer. When multiple connections are made, Windows has to know which connections to use to speak with another remote computer. For the TCP/IP or Internet Protocol (IP) data, this information comes from the routing table. This table stores lists of IP addresses and subnets (blocks of IP addresses) as well as indicates which adapter (or interface) Windows used to reach each of them.
Now, this is getting into some hardcore networking that only a few readers will be interested in; please don't think that you'll need to know about this tool (there will be no quiz next Friday). I'm discussing this only to get the details down for those few people who have a complex network setup and only need to know how to go to this information. You don't have to worry about routing unless one of the following scenarios is true:
You use a dial-up connection and a LAN adapter simultaneously.
You use multiple LAN adapters.
You use Virtual Private Networking connections, as discussed in Chapter 18, “Windows Unplugged: Remote and Mobile Networking.”
If you have trouble reaching an Internet destination and fall into any of these three categories, type route at the command line. You'll be shown a table that looks something like this:
===========================================================================
Interface List
0x1 ........................... MS TCP Loopback interface
0x2 ...0e c3 24 1f 09 3f ...... NDIS 5.0 driver
===========================================================================
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 202.201.200.190 202.201.200.166 1
127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1
202.201.200.160 255.255.255.224 202.201.200.166 202.201.200.166 1
202.201.200.166 255.255.255.255 127.0.0.1 127.0.0.1 1
202.201.200.255 255.255.255.255 202.201.200.166 202.201.200.166 1
224.0.0.0 224.0.0.0 202.201.200.166 202.201.200.166 1
255.255.255.255 255.255.255.255 202.201.200.166 202.201.200.166 1
Default Gateway: 202.201.200.190
===========================================================================
Persistent Routes:
None
There's a lot of information here, but for our purposes, we can boil it down to this: The entry for network destination 0.0.0.0 is the effective gateway address for general Internet destinations. This can be different from your LAN's specified default gateway, especially while a dial-up or VPN connection is active. That, in turn, may mean that you can't get to the Internet. If you have multiple LAN adapters, the issues are more complicated. Contact your network administrator for assistance.
Note
→ If the gateway address is incorrect after you've made a dial-up connection, see “Routing Issues,” p. 712.
Besides the utilities provided with Windows XP, there are some third-party tools that you can use to help diagnose your connection and gather Internet information. I'll describe three Web-based utilities and one commercial software package.
Ever wondered how to find the real-world transfer rate of your Internet connection? Intel Corporation has a nifty Web-based program to measure transfer speeds using a Java applet. Check out www.intel.com/personal/do_more/broadband/speedtest.htm. (Every time I put this URL into print, Intel seems to feel the need to change it. If you get a “page not found” error, search the Intel site for “broadband speed test.”)
Anyone registering an Internet domain name is required to file contact information with a domain registry. This is public information, and you can use it to find out how to contact the owners of a domain whose customers have sent spam mail or with whom you have other concerns.
Finding the registrar for a given domain name can be a bit of a bother. You can find the registrar information for any .aero, .arpa, .biz, .com, .coop, .edu, .info, .int, .museum, .net, or .org domain via the following Web page:
The search results from this page will indicate the URL of the whois lookup page for the associated domain registrar. Enter the domain name again on that page and you should be shown the contact information.
It's a bit harder to find the registrar associated with two-letter country code domains ending in, for example, .au, .de, .it, and so on. The InterNIC site recommends searching through www.uwhois.com.
You can find the owner of an IP address through a similar lookup at www.arin.net/whois. Enter an IP address to find the owner of the block of IP addresses from which the specific address was allocated. This is usually an ISP, or in some cases, an organization that has had IP addresses assigned to it directly.
As I discussed earlier, the tracert program investigates the path that data you send through the Internet takes to reach another location. Interestingly, data coming back to you can take a different path. Users of older satellite Internet service know this already as their outbound data goes through a modem, while incoming data arrives by satellite. It turns out that this can happen even with standard Internet service, depending on the way your ISP has set up its own internal network.
It's handy to know how the path data takes coming to you. If you record this information while your Internet connection is working, then if you run into trouble you can have a friend perform a tracert to you (you'll need to give him or her your IP address, which you can find using the ipconfig command). If the results differ you may be able to tell whether the problem is with your computer, your ISP, or the Internet.
You can visit http://www.traceroute.org for a list of hundreds of Web servers that can perform a traceroute test from their site to you. Don't be surprised if the test results take a while to appear as these tests typically take a minute or more.
If you want to be really well equipped to handle Internet and general networking problems, you can buy third-party utilities that are really much easier to use than the standard ones built into Windows. I really like WS_Ping ProPack from Ipswitch Software (www.ipswitch.com). This one utility packs almost all the TCP/IP tools into one graphical interface and adds other features such as whois for domain registration lookups, SNMP probing, and network scanning. The registration fee is $37.50 U.S. for a single-user license. I rarely use or like add-ons like this, but I use this program every few days for one reason or another, and it quickly made my “must have” list.
I have a DSL connection in my office, and one night it appeared that my Internet connection had stopped working. After a closer look, I saw that only downstream communication was affected, meaning my browser could contact Web sites, but information from the Web wasn't reaching my computer.
I first tried pinging my ISP at the gateway address of my DSL modem. It worked just fine. In fact, I could ping any site in the entire Internet but still could not view a single Web page. I called my Internet service provider and they found out that pings from their network into my LAN worked, too. The guy I spoke to suggested that I must have a software problem.
That didn't make sense to me, especially because everything was working fine just minutes before. Then I had a hunch. Ping, by default, sends very small packets: 32 bytes each, plus a few bytes of IP packet packaging. Requests for Web pages are very small, too (maybe 100 bytes). However, responses from Web servers are big and come in the largest packets possible—about 1500 bytes each. This meant the problem might not be the direction the data was taking. Instead, it could be the size of the data that was causing the problem: If there was a lot of interference on my DSL line, it could be that small packets would likely make it through between bursts of electrical interference, but larger packets would be much more likely to be garbled.
I vaguely remembered that ping has a bunch of command-line options, so I looked up “ping” in Windows Help and saw that I could increase the size of its packets with the -l option. Typing
ping -l 300 www.someplace.com
tells ping to send 300-byte packets. Aha! I found that only about 50 percent of these packets made the roundtrip. When I sent 500-byte packets, the success rate dropped to 10 percent. When I called tech support with this news, the guy at my ISP tried the same test, and got the same result when he tried to ping my computer from his network. Now, we knew that there was a physical problem that the ISP was responsible for fixing.
That problem was eventually fixed, but still every month or so my Internet connection seems to bog down. Usually, this lasts only a minute or two due to random Internet happenings, but sometimes it slows down and stays slow. When this happens, I ping the gateway address to see what the round-trip time is. For my connection, this is normally about 20 msec. For reasons I still don't understand, occasionally this jumps up to over 1000 msec (over a second!) and stays there. I have to power-cycle my DSL modem to get back to normal response times.
The moral of this story is that it pays to be familiar with your friendly neighborhood command-line utilities.