unbound NXDOMAIN TTL shared between records

[Daisuke HIGASHI]

Hi, Patrik -

> which also suspiciously seems to use the SOA TTL of 7200
> rather than the NXDOMAIN TTL of 18000

That is how negative cache TTL is calculated (by authoritative server).
RFC2308 reads:

  (Negative cache) TTL is taken from the minimum of the SOA.MINIMUM field
   and SOA's TTL.

Regards,
Daisuke HIGASHI