TTL for name servers

[Mark Andrews]

In message <CABUciRkVT6mBS0ZS3WL4tS7uTPgYNVBkOr890fsB9OoqP=CeOQ at mail.gmail.com>
, Alexander Gurvitz writes:
> Hi.
> 
> TTL returned by YOUR zone authoritative server will (at least should) be
> preferred by caches.
> 
> Matt Larson from verisign explained on these:
> 
> http://www.merit.edu/mail.archives/nanog/2004-07/msg00255.html
> 
> Regards,
> Alexander Gurvitz,
> net-me.net

TTL of NS records are complicated as the existance of the delegation
is covered by the parents NS records but the contents of the NS
records comes from the child zone.  Named looks at both TTLs to
determine when to remove the NS RRset.

https://deepthought.isc.org/article/AA-00691/

If you are wanting to workout when to decommission a nameserver take the
maximum of the two NS rrset after they have both been updated as when it
is safe to decommission.

Mark

-- 
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org