How to Use tracert to Diagnose Network Problems

Tracert (short for traceroute) is a network diagnostic tool that can be used to determine where network problems are located. This can be a useful tool to figure out why you can't connect to another computer over the Internet. This article explains how to use tracert to diagnose network problems on Windows. If you are interested in learning the technical details of how traceroute works, check the resources section.

Things You'll Need

• Microsoft Windows

Instructions

1. 

   Bring up the "Run" dialog box by clicking on Start, then Run. Alternatively, you can bring up the dialog box using a keyboard shortcut by holding down the Window key and pressing R.

2. 

   In the edit box next to "Open:" type "cmd" without the quotes and then hit enter. This will open the DOS command window.

3. 

   At the prompt, type "tracert www.google.com" without the quotes and hit enter.

4. Wait while the tracert runs. The output from tracert is in 4 columns. The first column is the "hop" number. Each "hop" is device that your network traffic gets routed through in order to travel from you to the destination. The next 3 columns are ping times. Ping time is how long it takes to send a network packet from you to another network device and back again. Ping times are measured in milliseconds. The fifth column is the address of the network device that the traffic is passing through (or stopping at).

5. 

   Look at the first item in the fifth column. In a typical home network, this hop is your router. If the tracert makes it this far then it means the connection between your computer and router is working.

6. 

   Look at the next few lines in the fifth column (I've blurred out some of my network identification in the image for security purposes). The initial hops after your router are your ISP's network, starting with your cable or DSL modem if it is a separate device from your router. The number of hops belonging to your ISP will vary depending on the ISP and the route of the network traffic. Notice that my ISP is Verizon and it's pretty clear which hops belong to them. If there are problems in these hops then I know it's Verizon's problem and can call them to complain.

7. 

   Look at the last line in the fifth column. In an situation where everything is working fine, this line will be your destination (www.google.com in our case). If things are not working, this will be the address of the network device that's having problems. If the address is not inside your ISP's network nor is it your destination then there's really nothing you can do other than wait and hope that whoever is responsible for the network device gets it fixed. If the problem is inside your ISP's network then you should call them. If the problem is with the destination host then you could contact them.

8. 

   Look at columns 2-4. This is where we will be able to see if there are any problems. Ping times should gradually increase as the hop count goes up. If there is a hop that has a dramatic increase in ping time (say, 100 ms to 700 ms) or has asterisks (*) instead of times then that hop is having problems. In the worst cases, all three columns will have asterisks and you'll start getting "Request timed out" messages.

9. 

   Be aware that there is a situation where things can be functioning properly but tracert will give you "Request timed out" messages. e-How is actually an example of this behavior. Network devices can be configured to ignore ping requests and when they do, you just get timeout errors even though other network traffic (such as web page requests) will work just fine. In this case, we see that the last successful ping was to DEMAND-MEDI. Since Demand Media owns e-How, we can deduce that there are no network problems between my computer and the e-How site. If I was having problems accessing web pages on e-How, with this information I could rule out my network connection to the site as the source of the problem.

Tips & Warnings

• If you get an error message of "Unable to resolve target system name ..." it means that your Domain Name Server (DNS) is not working and you most likely need to call your ISP about the problem.

Resources

• Wikipedia article on tracert