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[_] DNS resolving oddity

Craig Francis craig at craigfrancis.co.uk
Mon Nov 6 09:44:15 GMT 2017

True, but it’s been like this for over a week (took them a week to say everything is fine)... so I doubt they are making changes :-)



> On 6 Nov 2017, at 9:35 am, Amias Channer <me at amias.net> wrote:
> 
> Hello _,
> 
> 
> Low TTL is usually set when expecting to make a lot of changes, then you
> crank it back up again when settled
> 
> Cheers
> Amias
> 
>> On 6 Nov 2017 09:12, "Craig Francis" <craig at craigfrancis.co.uk> wrote:
>> 
>> Thanks for confirming Oliver,
>> 
>> I’m trying to help the company who (not surprisingly) had DNS issues last
>> week, and the setup seems odd (the 20s TTL seems wrong to me as well).
>> 
>> This was just the first time I’ve seen a setup where you could get another
>> Authority response when asking for an A record (i.e. after doing the NS
>> lookups, and being told who should be the authority for that domain).
>> 
>> And I’m running OSX as well, so not sure why I was needing the +noedns
>> flag.
>> 
>> Craig
>> 
>> 
>> 
>>> On 5 Nov 2017, at 10:59 pm, Oliver Humpage <oliver at watershed.co.uk>
>> wrote:
>>> 
>>> 
>>>> On 5 Nov 2017, at 17:45, Craig Francis <craig at craigfrancis.co.uk>
>> wrote:
>>>> 
>>>> We finally get the answer, but this seems a bit weird/broken to me...
>> yet somehow it works (for all?).
>>> 
>>> I guess your concern is that a DNS server that should be authoritative
>> for the domain isn’t returning an answer.
>>> 
>>> However, what it is returning (an Authority section) is exactly what
>> both the root and .com DNS servers returned. Therefore the client will
>> simply carry on following the chain and ask one of the servers in the
>> authority section, which as you noted works fine (on OS X I didn’t need the
>> +noedns flag).
>>> 
>>> So it’s slightly odd, but it’s all within spec. Of more concern is the
>> 20s TTL, which is insanely low. Whatever you’re doing that requires that
>> low a TTL, do it another way, cos that’s not really how DNS is meant to
>> work :)
>>> 
>>> Oliver.
>>> 
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