May 06, 2006Memorable DNS IPsComcast has ocassionally messed up its DNS servers - last year they had a series of systemwide DNS outages that lasted several days. (My Comcast DNS servers are 68.80.0.12 and 68.80.0.5.) Today Comcast DNS is being slow - but not out. That is good, because it means I can still get to Google and I can still use it to find other DNS servers. For future reference: if my DNS servers ever go out, I will use the following DNS servers with easy-to-remember IP addresses - thanks to AT+T and Level 3: Here in Pennsylvania, these servers are all just as close as Comcast's DNS servers to me, < 20ms ping, and they are serving DNS faster today. Update Apparently Reza also uses the same DNS IP addresses in Seattle with good results, which seems remarkable. Curious, I collected some roundtrip numbers to 4.2.2.1 from various computers I use:
The evidence seems to contradict the laws of physics. It takes 32ms for a photon traveling at the speed of light to bounce from the U.S. Northeast to the West Coast and back again; in practice you're doing extremely well if you can get through all the routers in twice that (for example my DC and CA computers have a 94ms ping time between them). But 3+13=16ms is much less than 32ms and a physical impossibility. Even with perfect zero latency routers and perfectly straight-line optical paths, a 16ms round-trip is twice as fast as possible. Perhaps there is a very clever predictive algorithm in San Jose that knows how to send a reply 40ms before receiving the request? Or perhaps Level 3 has installed top-secret quantum time-warp hardware at 4.2.2.1? Or maybe 4.2.2.1 is using Robert Boyd's magical erbium glass fiber? It turns out that 4.2.2.1 routed using "anycast," which is a kind of routing that lets servers distributed around the world to be assigned to the same IP address - something that is usually a no-no. Most big web servers use round-robin DNS for load-balancing, which is where there is more than one IP address that can answer to the same DNS address. But since you can't rely on DNS lookup to distribute load for DNS servers themselves, anycast is the alternative. Interesting. Update 9/5/2006: 4.2.2.2 was having trouble yesterday. For future reference, the OpenDNS servers are: And they are quite fast! (They also come with some weird features like anti-phishing redirect, etc, which is both a plus and a minus depending on what you want to do.) Update 9/23/2015: In recent years I've been using Google's DNS servers - also easy to remember. No redirections, and Google is serious about speed and security.
Comments
I had the same situation here in Seattle last year and switched to the same IP that you are using: http://rezabe.blogspot.com/2005/05/our-home-internet-is-much-faster.html Posted by: reza at May 6, 2006 01:34 PMThey all use IP Anycast - in otherwords, identical servers scattered around the network with the same IP. These IP's are announced- and their IGP choses the shortest path to the 'nearest' server. www.nanog.org has some nice preso's on DNS Anycasting. Posted by: Darrel at June 25, 2006 12:51 AMWe also use anycast at OpenDNS and with an account you can manage your preferences and have insight into the DNS unlike you've ever had before. It's powerfully cool stuff. Posted by: David Ulevitch at July 18, 2007 09:28 PMBelive it or not ping returns an average of 16ms to 4.2.2.1 - and that is from the United Kingdom As you say, strange but true Cheers John 12ms from Portland, Oregon Posted by: Somebody at July 30, 2008 11:27 PMI have been using 4.2.2.1 for a few years now as well and was talking to an apple rep a few days ago, who was also using the same dns servers. I decided to google the IP and found your site. FYI I had great speeds in locations across Japan, Guam, Hawaii, Canada and pretty much any location I was in. The IP is hard coded into my brain. Posted by: chimpoko at October 21, 2008 01:49 PMToday Charter communication's was having noticable DNS issues...so i called the tech department, Ran across your site looking for some history on these infamous DNS servers. Thanks. Posted by: mk at April 8, 2009 08:34 PMThis is the Googles free DNS service Posted by: Sachindra Kumar at March 4, 2010 03:15 AM@SK: no this isn't. Google is providing free DNS service on the IPs 8.8.8.8 and 8.8.4.4 Posted by: torzsmokus at June 17, 2010 05:09 AMtechnically still owned by LEVEL 3: 8.0.0.0 - 8.255.255.255 not google. do a whois look-up and see for yourself. Posted by: jonny rocket at February 12, 2011 12:56 PMTechnically, the 8.8.8.0/24 network is allocated to Google: Level 3 Communications, Inc. LVLT-ORG-8-8 (NET-8-0-0-0-1) 8.0.0.0 - 8.255.255.255 Thank you so much, like omg, so much help u have been... If you're using 4.2.2.1 - 4.2.2.6 (for awhile just 4.2.2.1 was not working) you will get dns hijacked/redirected to http://searchguide.level3.com/ when you visit a domain that does not resolve. Since it's a big part of the fabric of the internet, they didn't want to shut it down, so they're now trying to profit from it. In a way, I don't blame them, since so many people are using it worldwide. More details on tummy's article called famous dns server Posted by: Justin Goldberg at September 18, 2015 02:21 PMPost a comment
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