ICSI Netalyzr says "Unable to contact an IPv6 only site" because of OpenDNS

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    rotblitz

    "I would like to see what OpenDNS has to say about the complaints they list.

    1. Unable to access IPv6 only sites and
    2. issues with resolving unresolvable domains and transient failures."

    Not sure what OpenDNS want to say about this. But here is my comment as a user:

    1. This is not really true, but related to point 2. Many clients try first to resolve to an IPv4 address (A record), and if this is not successful (NXDOMAIN), another attempt is made to obtain an IPv6 address (AAAA record). Because OpenDNS almost return a valid (non-error) result for IPv4 lookups, this attempt for IPv6 is not made at all.
      The culprit is not really OpenDNS, but the client trying IPv4 first instead of IPv6. The solution is to change the priority, to look for the AAAA record first.
    2. Same as many other ISPs and public DNS services, OpenDNS uses NXDOMAIN redirection by default, i.e. in case of querying a non-existing or badly DNS-configured domain it doesn't return an error, but redirects you to a page (called The Guide) showing search results and some ads. This is what the service gets paid for.
      You can disable NXDOMAIN redirection while disabling typo correction under advanced settings at your dashboard, but then you lose content filtering with a free account. If you want both, content filtering and no NXDOMAIN redirection, then you can upgrade to OpenDNS VIP.

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