Minimum TTL?

Reindl Harald h.reindl at
Fri Feb 9 07:21:48 UTC 2018

Am 09.02.2018 um 07:02 schrieb sthaug at
>> I think what is "OK" is up to each administrator.
>> Obviously the zone administrators have decided that they want people to
>> use the 2s TTL.
>> That being said, it is up to each individual recursive server operator
>> if they want to honor what the zone administrators have published, or if
>> the recursive administrators want to override published desires.
>>> It really is something for the zone owner to consider.
>> Yes and no.  Yes it's up to the zone owner to consider what intentions
>> that they want to publish.  No, the zone owner has no influence on how I
>> operate my servers.  I choose how I operate my servers.
> Yesterday I measured, on our busiest resolvers, the amount of replies
> with TTL=0 the resolvers received (from the authoritative servers).
> Turns out we receive around 2.3 percent replies with TTL=0. This is
> a percentage I can live with, and I see no reason to artificially
> inflate the TTL.
> That being said - if the percentage had been significantly higher, I
> would feel it was perfectly reasonable to set a minimum TTL of for
> instance 10s. I agree that this is a decision for each operator.
and i can tell you from where they are coming:

CISCO router with "DNS-ALG" between primary and slave writing in front 
of every CNAME explicit a TTL 0 statement - was there and it takes a 
long time until you realize that your slave repsonds with differnt data 
as you configured

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