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This troubleshooting "hints" guide is not meant to be an all inclusive 100% complete guide. These are some of the steps our engineers and analysts will take when troubleshooting an internet connectivity problem. Most times, these steps will result in trouble resolution. Our hopes are that by publishing these steps, we can help to educate our clients, and provide them with a means to resolve the problem with no cost and minimal time invested. So with that all said, there are many problems that can plague broadband users. Many of these can be fairly simple and inexpensive to troubleshoot and resolve if you know what to look for. Network Basics
Power it OFF and ON
Rule Out Your Router
Use Windows IP Tools
To do this, first open a COMMAND window on your computer. Click on START and select "Run". This will open the "Run" dialog. Type in "cmd" and click OK. Then type in "IPCONFIG/ALL" and hit the ENTER key. You will see something like this:
The results will include - among other things - your IP Address (for your PC), your default gateway, and your DNS servers. To access an internet site, [a] your IP protocol in your PC must be working [b] you must be able to communicate with your gateway [c] your gateway must pass along your requests to the DNS (Domain Name Server) to resolve the name (i.e., www.yahoo.com) to an address (i.e., 216.109.112.135) and [d] the web server with that address must be working properly. To test each of these "layers", all you have to do is "ping" each of these addresses. If you get consistent replies, that element is most likely not the problem. PING yourself (don't worry, you won't go blind)
You do this using the local "IP Address" taken from the IPCONFIG results. PING the gateway
This runs a test to your router or broadband modem. PING the DNS
This will verify that you have connectivity to your domain name server. In some cases this DNS address is your broadband modem. Other cases, it may be a server on the internet. If you see that the DNS address is the same as your gateway, you can try to ping 4.2.2.2 which is a public DNS owned by a large internet service provider, and should return positive results. This will verify connectivity to the public internet. PING an internet URL (domain name)
For example, if you select ping the internet YAHOO.COM, you will actually be pinging the public IP address that the DNS returns. The DNS replies to your computer after translating yahoo.com to it's public IP address "216.109.112.135" and your computer then sends it's request to that IP address. This will tell you if you are [a] connected to the public internet, and [b] if the DNS is working. Successful ping results look something like this:
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INTERNET PROBLEMS
First it helps to understand the basics of home networking and internet access. Your home network includes any and all computers, network printers, routers, wireless access points, and/or modems in your home. Your computers are typically not connected directly to the public internet. Your local network provides NAT (Network Address Translation) service (a service that helps hide the IP addresses of your local network devices behind one public IP address, and provides "one to many" relationships between public and private IP addresses). Your local network is then attached to an ISP (Internet Service Provider) that provides DNS (Domain Name Server) and internet routing services. Some broadband modems (DSL or cable modems) use NAT, and so do most home and small office routers. NAT is the basis of their firewall protection layer. Hackers encounter that public IP address and cannot easily see your computers behind it in order to it to hack into them. The diagram above shows a typical home network with multiple network devices. Your network may be far more or less complex. It would be good to draw a diagram of your home network, showing what devices are connected where. 
When in doubt, power down and restart. This age-old solution still applies when it comes to broadband modems. Occasionally a modem may fail to properly update when your ISP assigns a new IP address, gateway or DNS. In any case, a simple unplugging and replugging of the power cord (or a 10-second flick off of the power switch if you have one) should be sufficient to reset the modem and have it properly redetect all information necessary from the ISP. Remember to be patient and wait for a couple minutes after everything restarts. You can apply the same principle to your router, but make sure you wait until the broadband modem has finished it's restart cycle. Same with your PC - I am sure you have had some technical support genius tell you to power it off and on again - this may sound silly, but it may solve the problem too. 
One way to do this is to unplug the wire running to your router/switch from the modem and plug it directly into the PC, thus taking the router out of the equation. If this suddenly cures the problem, you know you're fighting a router issue, and NAT conflict is one likely culprit. Remember to wait a couple minutes before retesting, as some routers take 1-2 minutes to completely restart. If you are still unable to connect, it is probably time to call your internet service provider to make sure your internet access is up and running. They will want you to be plugged in directly, so this would be a good time to do this. 
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