On Sat, 2017-07-01 at 11:37 +0200, Nicolas Kovacs wrote: > Le 01/07/2017 à 11:00, Pete Biggs a écrit : > > That is controlled by the TTL (time to live) entry. A DNS server must > > refresh it's cache within the TTL for the entry. Using the '-a' option > > to host will give you more information: > > So I would have to use the -a option with the old DNS server, to know > their TTL. Yes, or use dig or something else that shows the TTL > I'm also wondering if some DNS server don't override the TTL > and keep the information longer. I remember such a case where the DNS > server of the french provider Orange kept a stale DNS information forever. > The TTL is part of the DNS record so no, they shouldn't override it, in the same way as they shouldn't override the A record or MX record. That doesn't mean that some providers don't do it "for operational reasons", but it's a stupid thing to do and will basically, literally, break the internet. P.