question on TTL

[dani]

Hi,

Which DNS server triggers the countdown for a DNS records
TTL?
Is this only the DNS server authorititave for the record
or can this also be for example a caching-only DNS Server
(the TTL starts from 100% again)?


Thank you, Dani

 

[Jonathan de Boyne Pollard]

d> Which DNS server triggers the countdown for a DNS records TTL?

A "countdown" is not "triggered" by a particular server. The decrementing of
TTLs happens on all cached resource record sets and begins as soon as they
enter a cache.

 

[Michael Johnston [MSFT]]

Only servers that are authoritative for the zone or record will report a TTL that is 100%. DNS servers that cache the record, will return a TTL for the remaining
time of that record. If they didn't, records could potentially be cached forever. That would be a very bad idea.

Thank you,
Mike Johnston
Microsoft Network Support

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