DNS reply ADDITIONAL SECTION data with MX lookup ?

LaMont Jones lamont at security.hp.com
Wed Jun 21 17:59:10 UTC 2000

>   I would like to optimize dual-mode (IPv4/IPv6) DNS lookups so that if
>   I get something for the ADDITIONAL SECTION, I could trust it to be of
>   complete data, and not to go to ask for same data again explicitely.

As I understand it, the answer is yes and no...  BIND will return
all or none of a particular RR type that it has in its cache (but I don't
think that AAAA and A are the same RR types, so you could just get A RR's,
when AAAA RR's exist, but I'm guessing there.)

However, the root nameservers only allow one IP per hostname, which means
that if you query a registered-but-dual-homed hostname against the roots,
then you'll get back partial information.  (See palrel1.hp.com when looked
up against the root servers, vs what you get from an authoritative
nameserver, for one example.)


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