"Traceroute" is a command-line tool which allows you to see the route data takes between your PC and a target server or website. It is useful for diagnosing connection issues, as it indicates where the data is being stopped.

To run traceroute on a Windows PC:

1) Go to "Start" > "Run", and type "cmd"

2) In the Command Prompt, type "tracert [insert your domain name, server or ip address]" and press "return"

On Linux systems:

1) Open a Terminal

2) Type "traceroute [insert your domain name, server or ip address]" and press "return"

On Apple Mac OS have two choices, firstly you can:

1) Open Network Utilities

2) Select the "Traceroute" tab, enter the details of the target, and press "return"

or go through a Terminal like Linux:

If you choose this option, you will get an output like this:

$ traceroute google.co.uk
traceroute to google.co.uk (173.194.41.152), 30 hops max, 60 byte packets
 1  192.168.1.1 (192.168.1.1)  0.130 ms  0.117 ms  0.110 ms
 2  185.24.99.49 (185.24.99.49)  2.851 ms  2.854 ms  2.872 ms
 3  188.65.116.33 (188.65.116.33)  0.388 ms  0.506 ms  0.440 ms
 4  router-002.sl5.misp.co.uk (91.146.104.2)  16.921 ms  17.005 ms  17.028 ms
 5  195.66.224.125 (195.66.224.125)  1.548 ms  1.526 ms  1.526 ms
 6  209.85.245.112 (209.85.245.112)  16.859 ms  1.519 ms  1.490 ms
 7  72.14.238.55 (72.14.238.55)  1.944 ms  2.048 ms  2.234 ms
 8  lhr08s03-in-f24.1e100.net (173.194.41.152)  1.501 ms  1.464 ms  1.480 ms

This tells us what networks and routers the packet is routing by to reach google.co.uk, and the times it takes to get there. If there are stars instead of times for a hop, that means the hop timed out (or the router does not accept ping packets).

For more information on traceroute, check out this Wikipedia article.