auth-nxdomain yes

[Gordon Freeman]

 >> I'm  hoping the answer is yes, so that once an NXDOMAIN response  is
 >> received by the name server, it will  not forward repeated queries for
 >> that  same name, at least for as long as the negative cache TTL. 
 >
 > Named does that by default.  Not all authoritative sources however
 > provide a cachable negative answer.
 
But that's not what I'm seeing.  If a client sends 100 queries for a non-existent name to its nearest name server, all of them are forwarded on up.  What I want is for the name server to cache those NXDOMAIN answers so even if a client is slamming my DNS, my server is not in turn hammering those name servers upstream.