The other day, my Internet connection went down — well, I didn’t see it go down but, when I got back from work that day, I couldn't browse anywhere. And, what would often help in the past would be to reboot my cable modem; so, I tried that about three or four times (and, really, I should have caught on after the second time). Comcast hasn’t been incredibly reliable for me — they tend to go down every couple months — and I just chalked this up to their usual ineptness.
I then noticed a curiosity — my IM client was still online. And I could still read my mail. But I couldn't browse the web (whaa?). I wondered for a moment whether Firefox was acting up and so I tried loading an ftp client to test my connection. (You thought I might load IE for that? Not if I can help it ;).) Sure enough, FileZilla couldn't connect anywhere either. Then it hit me: my DNS had probably gone wonky. That would explain why I couldn't browse anywhere but my most common Internet apps still held up — those ip addresses were cached by my OS.
At that point, I ran “ipconfig /all” and then pinged the DNS servers to which I was assigned. To no surprise, they both timed out. Then, on a hunch, I tried loading Google and I was actually able to make it there (since I suppose its ip address was one of those in my cache). I then tried searching for “alternate DNS servers”. There were quite a few hits but, of course, I couldn’t see any of them since those sites weren’t in my existing DNS cache (d’oh!). It then dawned on me that I could view the Google Cache of those pages; and, while the pages probably wouldn't look pretty, that would hopefully allow me to get the info I needed.
Indeed, Google Cache worked nicely and I found some alternate DNS servers that I could use. I popped those in my settings and I was up and running again. However, I realize now that I could have made things easier on myself by keeping a few spare DNS servers on hand — before they actually went down. In any case, while there are dozens of DNS servers which are suitable, some that were mentioned consistently were the 4.2.2.x series (4.2.2.1 through 4.2.2.6).
I did an nslookup on those ip addresses and they came back as Genuity.net and GTEI.net servers. Perhaps ironically, I can’t load either of those domains right now, otherwise I’d include a sentence about who each of those companies are ;). But, with such low-numbered ip addresses, I presume they’re of some importance within the InterWeb. In any case, one of the comments on Digg.com [*] offers these instructions for adding DNS servers in case you haven’t done that kind of thing before:
Click on “My Computer”. Click on “My Network Places”. Click on “View Connections”. Right click on the connection that supports your Internet connection and go to “Properties”. Double click on the Internet Protocol TCP/IP option. Make sure “Use the following DNS server address” is selected, and input the above recommended DNS.
To check go to “Start > Run > “cmd” ”. Type in “ipconfig /all” and you should see the DNS you input where it says “DNS”.
[*] On a side note, what is Digg, anyway? Pages within digg.com have been coming up in my search results more frequently recently but I can't quite wrap my head around what the site is about. Something about folksonomies, I’m guessing.
Anyway, before adding those DNS servers, you may as well ping each of them to see which of them are fastest for you. If you go through all six of them, just pick (say) the two with the lowest ping times. Granted, it’s all a matter of milliseconds but every little bit helps ;).