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Domain Name System (DNS) troubles: DNS Servers Down?

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  1.  
    • CommentAuthoryokahoma
    • CommentTimeJun 22nd 2012
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    Been running a year with no troubles and now today DNS is not resolved, can't ping 208.67.222.222 or 208.67.220.220. Anyone else?
  2.  permalink
    Administrator
    Can you open a ticket and send us the traceroute output to each server? We are currently investigating an issue with Comcast in the Minnesota/Chicago area.
    Thankful People: zelus
    • CommentAuthormillerc2
    • CommentTimeJun 22nd 2012
     permalink
    Thank god its fixed now. That was a real pain.
    • CommentAuthoryokahoma
    • CommentTimeJun 22nd 2012
     permalink
    I just ran the traceroute and it's back up now. I'm in Minnesota with Comcast as our Primary ISP.
    • CommentAuthoryokahoma
    • CommentTimeJun 22nd 2012
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    Any idea what the issue was and if it's fixed? I'd like to set our DNS back to opendns servers.
    • CommentAuthorsalimpert
    • CommentTimeJun 22nd 2012
     permalink
    I'm also in Minnesota with Comcast as ISP, and I am still down. Had to change DNS servers to Comcast's ( 75.75.75.76 and 75.75.75.75 ). Would like to change back to OpenDNS servers ( 208.67.222.222 and 208.67.220.220 ) Can OpenDNS broadcast an email when the problem is fixed?
    • CommentAuthorcvananda
    • CommentTimeJun 22nd 2012
     permalink
    We support several dozen clients with Comcast in the Twin Cities and found that as of this morning, Comcast started to block *all* outbound DNS queries except ones that use their DNS servers. This meant OpenDNS didn't work, other DNS services didn't work, and neither did queries to root DNS servers. We had to switch everyone over to use Comcast DNS servers for now, but after reading comments on here stating it was working again for some people I just tested a few sites and it does appear to be working again.
    • CommentAuthormaintenance
    • CommentTimeJun 22nd 2012 edited
     permalink
    That's Comcastic!

    yokahoma:

    "Any idea what the issue was and if it's fixed?"

    The issue is Comcast denying use of third-party DNS. Some parts of their network are permanently like this, last I heard, and some with no opt-out ability.

    However, people up the thread from you say it is working for them. All you can do is try it. There is no way OpenDNS can know what is happening at your exact internet connection. I'd bet even Comcast could not definitively answer your question without having you test.

    Test without all the horrendous trouble of changing DNS addresses first?
    nslookup -type=txt which.opendns.com. 208.67.220.220
    or
    dig -t txt which.opendns.com 208.67.220.220

    When you change DNS addresses back, don't forget to flush browser and local resolver caches.

    edit: For future reference:
    http://system.opendns.com/
    Will tell you if servers are down.
    •  
      CommentAuthorjedisct1
    • CommentTimeJun 22nd 2012
     permalink
    Administrator
    Don't forget that OpenDNS resolvers also listen to ports 443 and 5353, both on UDP and TCP.

    You can use a local DNS caching resolver to forward queries to OpenDNS on these ports. Or use the dnscrypt proxy, which also allows alternative ports.
    • CommentAuthorsalimpert
    • CommentTimeJun 22nd 2012
     permalink
    I spoke with a Comcast representative who took time to investigate this issue. After returning, the representative said Comcast has not blocked 3rd-party DNS servers, verified the strength of my signal, reset my cable modem, and asked me to call back if I had any further problem using the OpenDNS servers. They would work with me to use the DNS service I wanted.

    I have had several technical support interactions with Comcast, and I have found their tech support to be very knowledgeable, professional, and sincere in their effort to resolve my issue to my satisfaction. I doubt Comcast has any malevolent intention.

    I will return to specifying the OpenDNS servers and I will post further comments here should I have any problems.

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