Alternate DNS Servers

Posted on by Ashley Bischoff

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 ;).

22 thoughts on “Alternate DNS Servers”

  1. In windows 2000, XP, and 2003, you can add more than 2 DNS servers. Put them in the order of fastest first, slowest last, and windows will try the first one for every hit, dropping to the second and third if the primary DNS is not available. You could put first the DNS servers from your ISP which are probably the fastest (fewest number of hops) followed by others to serve as a backup. That way, when Comcast’s servers come back up, your computer will automatically start using those DNS servers, without you having to further dink with your settings.

  2. That sounds like good advice, Mike. However, from what I’ve read, Comcast only uses two DNS servers nationwide (!). So, of course, when those went down, it took their entire network went down. But, more than that, those DNS servers could be in Oregon for all I know and I can’t be sure they really would be faster than a 3rd-party DNS server :-/.

  3. so M$ Loseblows is now a caching name server?

    instead of using FileZilla as a network diagnostic tool one might consider some gems like mtr and dig. although presumably all of these would’ve worked had you fed them an IP address instead of a name to resolve.

  4. I actually used this for another purpose – my ISP cached name server settings for one of my domains, and I was in a hurry to work with the new host, so on my ADSL modem i changed the primary DNS server to 4.2.2.1 and flushed the local cache and it was all sorted. What is really remarkable is that 4.2.2.1 is FASTER than my ISP’s DNS.

  5. The DNS server at 4.2.2.1 is part of a group with similar addresses at 4.2.2.x where x is 1-6.

    You may want to ping them all and see which one is fastest for you. 4.2.2.2 is fastest for me and …1 is slowest by more than a few ms.

  8. 4.2.2.1, 4.2.2.2, 4.2.2.3, 4.2.2.4, 4.2.2.5 belong to Level3, a CLEC are are available for anyone to use. They aren’t the fastest, not the best, but they are easy to remember and they always seem to work. I personally would not recommend you use them on a daily basis since OpenDNS and your own ISP DNS servers generally are faster and better but when all else fails, Level3’s DNS servers are there, reliable, free etc.

  10. No. The 4.2.2.x servers ARE Anycasted, but they ARE owned by L3, not “many different companies/organizations”.

    Genuity, GTEI, etc are all L3, not other companies.

  16. BTW, Genuity is a company that manufactures genetically modified seeds. Their website loads without problems if you use their dns.

  17. Just so you know those backbone addresses are for the Go-mint and the copses. You will all be pushed to these select IPs for DHCP so they can track you moves. True DHCP will die. Static IP and select (read traceable) DHCP is the way of the future.

  18. Genuity was originally a dot com-era brand of the old GTE (now named Verizon), and offered business-class internet services (hosting, VPN, etc). Thats why a lookup on these IP’s sometimes returns an owner of GTEI (GTE Internet). I never followed Genuity after 2001 or so (which is when GTE sold it I believe) but it would make sense that L3 owns the brand now.

    Should those 4.2.2.x servers ever go down lots of things will go boom. 4.2.2.1 and 4.2.2.2 are so reliable that many consultants/techs/admins/etc (including myself) use them as a test or temporary work-around for less-reliable DNS servers. Unfortunately, like most work-arounds, many of us forget to change them back or find a better fix. I frequently find 4.2.2.1 and its siblings configured in DNS server forwarding lists, home gateways, mail filters, even global Exchange org configurations.

  19. As someone who used to be at GTE/Genuity/L3, 4.2.2.x predate Genuity. They’re actually part of the heritage of BBN, or “the people who build the Internet”. As far as I’m aware, they are the first implementation of the anycast idea in DNS. If my memory serves me — and it’s been many years — every single server, and there are many, is BGP peered into the network so that it will benefit from the overall routing architecture. As such, overall, it achieved 100% uptime for many years. Last I knew, there had been no downtime that was actually attributable to the server clusters, and instead it was all caused by peering issues.

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