Try a Wired Connection

If you are connecting to the Internet using a wireless connection, usually on a laptop, then the culprit in your loss of connection may just be a loss of wireless. The easiest way to check this is to plug your computer directly into your router and see if it can reach the Internet over a wired connection. If this works, then wireless loss is to blame. This could result from a problem with your wireless adapter or your router, so check the relevant instruction manuals and the manufacturers' websites for potential issues.

Restart your router

It is very common for router issues to cause Internet failure. As with many technology problems, rebooting often fixes the issue. Most routers do not come with an on/off switch, so you will need to physically unplug the machine from its power source. Wait about 30 seconds before plugging the router back in. If this fixes your issue, excellent! If not, read further.

Restart your modem

Of course, if your modem and your router are the same machine, you have already done this. However, if you have a separate modem and router, unplugging the modem can fix some connectivity issues. Cutting power to the modem forces it to reboot and resync with your provider's home office, which can clear up any difficulties the modem had been experiencing. Usually, this will solve immediate connectivity problems, but the trouble will return later.

Bypass the router

Again, this step is only relevant when using a separate router and modem. Try plugging your computer into the modem directly with an Ethernet cable. If this gets you Internet, your router is almost certainly to blame for the issue. If restarting the router did not fix the problem, it is time to move on to more drastic measures.

Reset the router

All routers include a reset button in case of serious connectivity issues. In order to prevent users from accidentally resetting their routers, this button is usually very small, needs to be pressed with a toothpick or similar object, and must be held down for some length of time to actually force a reset. Consult your router's instruction manual for detailed information on how to reset. If plugging your computer directly into the modem gives you Internet, and resetting the router does not fix the problem, it may be time to replace your router.

Reset your IP address

Resetting your IP address can resolve many tricky connection problems. Even if this solution does not work, it will cause no further damage. Open the command prompt by clicking on Start, then Run, and then typing in cmd or cmd.exe. Type ipconfig /release into the command prompt, followed by ipconfig /renew to reset your IP address. Renewing your IP address can fix issues that prevent your computer from communicating properly with your Internet Service Provider. If that does not work, other steps in the command prompt may help.

Flush the DNS Cache

Your computer's Domain Name System, or DNS, stores IP addresses and other domain name results in order to speed up future browsing. Some connection issues result from bad data stored in the DNS, which must be cleared in order to connect properly. Again, open the command prompt by clicking on Start, then Run, and then typing in cmd or cmd.exe. Type in ipconfig /flushdns to flush the DNS Cache. As with resetting your IP address, this operation can do no real harm.

Note that in Windows Vista and Windows 7, flushing the DNS Cache requires administrator privileges. As such, you will need to open the command prompt in administrator mode. To do this, type cmd into the Start Menu's search box and right-click on the program cmd when it appears in the search results. Click on the Run as administrator option, then type in ipconfig /flushdns as above.

The Ping Test

Using the command prompt's ping functionality can help diagnose connection problems. Get into the command prompt as detailed above, then try to ping the router's IP address, e.g. ping 192.168.1.1.  If you do not get a reply, there is a connectivity issue between the computer and the router. If you do, move on to the next step.

Use the command prompt to ping an external site by IP address, for example ping 4.2.2.1. If you do not get a reply, your router is not connecting to the Internet. Access your router through your web browser and check its status. Additionally, try rebooting the router and your computer.

If you can ping an external site by IP address, try to ping by name, e.g. ping www.google.com. If that does not get a reply, try an IP reset and DNS flush as detailed above. If that does work, your Internet connection is fine. If you cannot browse the Internet, check your web browser's settings for the issue.