Ping It!
DNS servers work like a giant table. On one side is the URL and on the other side is hte IP address. When you type in a URL it basically goes through the table, finds the URL, and then redirects you to the IP address associated to it. This is all a very high-level explanation, but basically DNS servers take the URL and make it an IP. If you think your DNS servers may be down, simply pop open your command prompt or terminal and ping this address: 74.125.127.100

That address is the default address for Google’s servers, which respond to ping (unlike the Mircosoft ones).

To ping it, just type: ping 74.125.127.100

On windows it will send out 4 packets by default and in Linux, it will keep sending them until you force stop with CTRL+C

If everything goes well (you’ll receive a little report at the end on windows) you’ll know it’s your DNS. This is because if we bypass the DNS and use the IP directly, we can see that it works fine.

Fix It!
This is a little more complicated. In order to fix it you’ll need the help of something else. Since the only problem is your DNS server, it stands to reason that changing it will solve the problem. However, picking a good DNS is a little harder, since you are trusting them to always direct you to the same place. If, for example, it was a malicious user running their own DNS setup, then they could redirect you anywhere they wanted, regardless of what address you typed into your browser. I’d suggest OpenDNS. They’re great, they’re fast, and they’re probably the most reliable (short of connecting directly to the web’s DNS system – where every DNS server connects to)

If you are behind a router, then you can keep reading, however, if you have a direct connection to the internet, then I suggest you head over to OpenDNS and get started there. They’ll walk you through setting it up regardless of your connection type.

Configure Your Router
When you’re going through the website at OpenDNS, they will give you IP addresses of their two DNS servers that you can connect to. Note these down. And keep going. You may as well make an account because OpenDNS allows for web-stats to be monitored by you. Once you’re done you’ll want to connect to your routers web interface. Depending on your router, the default address for this will change. For me it was 192.168.1.1 and it will be the same for almost every Linysys router. Since I’m running DD-WRT, my interface will look quite a bit different from yours, but the setup is still essentially the same.

The section you are looking for is this:

You’ll want to change it to the ip address of the DNS server that OpenDNS gave you.

Then just hit the save button and you’re all done. From now on any outages you get either won’t be DNS related or OpenDNS will let you know as soon as it happens, so you’re not sitting around wondering why you can’t Google.