[ntp:questions] IPv6 vs IPv4 look-ups (Was: Re: http://www.ntp.org/ => a blank page?)

Martin Burnicki martin.burnicki at meinberg.de
Thu Mar 5 14:26:55 UTC 2009

Rob wrote:
> Steve Kostecke <kostecke at ntp.org> wrote:
>> On 2009-03-05, Martin Burnicki <martin.burnicki at meinberg.de> wrote:
>>> The IPv4 address is used only after the IPv6 address has timed out, even
>>> though (as far as I understand it) the DNS server first returns an IPv4
>>> address, then an IPv6 address:
>>> # host support.ntp.org
>>> support.ntp.org has address
>>> support.ntp.org has IPv6 address 2001:4f8:0:2::23
>> On my LAN I see:
>> $ host support.ntp.org
>> support.ntp.org      A
>> To resolve the IPv6 address:
>> $ aaaa support.ntp.org
>> support.ntp.org      AAAA    2001:4F8:0:2:0:0:0:23
>> Both 'host' and 'aaaa' are a part of the Debian host package. The
>> version I have installed is:
>>||/ Name         Version       Description
>> ii  host         20000331-9    utility for querying DNS servers
>> If it matters I run a local name-server and do have a 6-to-4 tunnel.
> That does not matter.  The protocol you use to query the nameservers
> (IPv4 or IPv6) has no influence whatsoever on the results returned from
> the queries.  Those results are only influenced by the queries being
> made and the entries in the zone.
> So, your "host" program asks only for A records.  Mine asks both A and
> AAAA.  (and MX as well)
> Your "aaaa" program (which I don't have) asks for AAAA records.
> This is all not very relevant for the result in the webbrowser.
> It depends on what queries the webbrowser makes, and what it does with
> the results.

That's also what I understand how it works.

Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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