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Identifying and Troubleshooting DSL/Router Networking Problems

This information is provided to assist you with networking problems, it is offered free and without any guarantee.

To view all current TCP/IP settings from your PC, do the following:

1. Open a comand prompt in DOS.
2. Click the Windows "Start" button and select the "Run..." option off the menu.
3. A little window should open just above the "Start" button. (see Figure 1 in attached Word Doc.)
4. Type "cmd" (without the quotes) and click the "OK" button.
5. A black DOS window should open up. (see Figure 2 in attached Word Doc.)
6. In the DOS window type the following "ipconfig /all" (without the quotes) and hit the "Enter" key. This will display your LAN information (local area network).
• Some text will appear in the DOS Window.
• Look for the following words "IP Address", "Default Gateway", "DHCP Server" and "DNS Server"
• The "IP Address" (the numbers to the right) identify your PC over the LAN (local area network). These numbers are assigned to your PC by the "DHCP Server" in larger networks, although XP will self-assign numbers without network service.
• The "Default Gateway" is the path way out of your network - how your PC gets to the internet, or the WAN (wide area network). In larger networks there may be several hops before you reach the WAN.
• The "DHCP Server" is the LAN (local area network) controller or managing device. In many home wireless networks, this is the Cable/DSL router. In medium and larger sized networks it may be a DC or user server.
• The "DNS Server" is the traffic directing device, it tells your PC where to go, literally. DNS services direct computers to other computers. In larger networks there will be several DNS servers. In many home wireless networks, it's the DSL/Router again.
7. Cable/DSL Routers usually have the same four networking tools on them ("IP Address", "Default Gateway", "DHCP Server" and "DNS Server"), which are a different set of numbers than the ones that belong to your ISP's Network. Your Cable/DSL Router stores the ISP's routing information, which is accessable by login into your Cable/DSL Router.
• How to access the Cable/DSL Router: Open a browser and type "http://" and the "Default Gateway" numbers from step 2 above (i.e. http://192.168.1.1).
• You should see a login & password box - login to the Cable/DSL Router.
• Once you login to your DSL/Router, you can see these four numbers from your ISP (print them or write them down).

Now return to your DOS window and type the word "ping" (without the quotes) then hit the space-bar and type one of the four sets of numbers you just printed or wrote down from your DSL/Router. Now hit the "Enter" key and the DOS window should respond with several lines of code that start with something simuliar to this:

C:\>ping 64.233.167.104
Pinging 64.233.167.104 with 32 bytes of data:
Reply from 64.233.167.104: bytes=32 time=14ms TTL=250
Reply from 64.233.167.104: bytes=32 time=14ms TTL=250
Reply from 64.233.167.104: bytes=32 time=14ms TTL=250
Reply from 64.233.167.104: bytes=32 time=16ms TTL=250
Ping statistics for 64.233.167.104:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 14ms, Maximum = 16ms, Average = 14ms

If you don't get a "reply" from each of the four numbers, then there is something wrong with the network going to your ISP.

What to do if you can't surf the internet?

The first troubleshooting step is to "reboot" the Cable/DSL Router and allow it to re-initiate communications with the ISP's equipment - this usually solves most problems, especially if the network was working previously. If you have Window XP or Windows 2000 Professional, then your PC will automatically connect to your Cable/DSL Router about 1 minute after you reboot the Cable/DSL Router. (For older operating systems Windows 95, 98, or ME, just email me back and I'll teach you how to "release" and "renew" network settings).

Troubleshooting the Network:

1. Ping you network card at 127.0.0.1 (this always the same IP Address called "loopback") It should reply quickly.
2. Ping your Cable/DSL Router - use the "Default Gateway" from step 2.
3. Ping your ISP's "Default Gateway" from step 3 above.
4. Ping a known web site like Google - "ping www.google.com"

If any of those fail to respond then attempt a "trace route" to that same number. A "trace route" will display the number and name of each network object on the line, until it hits the trouble spot. To do a "trace route", go back to your DOS window and type "tracert" (without the quotes) then hit the space-bar and type the failed number. Watch as the network items respond one after the other until it fails (a failure is revealed when a network item or server displays "Request timed out" on the DOS window). The last responding network IP Address is where go to find the network problem...something on that device is not "pointing" to the next device properly. Next week we'll cover NATs (network address translation), which is how all the PC's on your network can surf on the same Cable/DSL Router.

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