ttl delegations question

[Barry Margolin]

In article <c7r1q0$1c05$1 at sf1.isc.org>,
 Matus UHLAR - fantomas <uhlar at fantomas.sk> wrote:

> Hello,
> 
> there are some domains that have TTL for their own records lower than TTL
> for glue records in their superior domains. e.g.:
> 
> uhlar at fantomas% dig ns documentum.com. @a.gtld-servers.net
> [...]
> documentum.com.         172800  IN      NS      ns10.documentum.com.
> documentum.com.         172800  IN      NS      ns11.documentum.com.
> [...]
> ns10.documentum.com.    172800  IN      A       198.182.5.170
> ns11.documentum.com.    172800  IN      A       198.182.5.174
> 
> uhlar at fantomas% dig ns documentum.com. @198.182.5.170
> [...]
> documentum.com.         3600    IN      NS      ns10.documentum.com.
> documentum.com.         3600    IN      NS      ns11.documentum.com.
> [...]
> ns10.documentum.com.    3600    IN      A       198.182.5.170
> ns11.documentum.com.    3600    IN      A       198.182.5.174
> 
> I'd like to ask, if BIND searches for e.g. MX record of documentum.com.
> domain, which TTL does it use? 

It uses the TTL of the MX record, which could be different from the TTL 
of the NS records (but isn't in this case).

> 
> in first lookup, bind receives NS and A records with TTL 172800,
> in second lookup it receives the same NS and A records with TTL 3600.
> 
> I'd like to know, which ttl is used in both cases? is it always the
> longer/shorter? Does TTL from zone override the glue TTL? 

Any record coming from the authoritative server takes precedence over 
the record from the parent server.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***