DNS ROOT understanding

Jonathan de Boyne Pollard J.deBoynePollard at Tesco.NET
Thu Nov 18 04:43:37 UTC 2004

JR> [...] if your name server is well-behaved, it will only
JR> communicate with a root server 4 or 5 times a week: every time
JR> it queries for a domain name in a TLD that hasn't been cached
JR> already.

JdeBP> Wrong. It will also communicate with a root server once
JdeBP> each for _every individual_ domain name looked up that
JdeBP> isn't under one of its delegated TLDs (which will
JdeBP> include a wide range of things from the ever-popular
JdeBP> "localhost.localdomain." to single-label "AAAA" lookups
JdeBP> generated by the broken search path mechanism in
JdeBP> IPv6-aware GLIBC), and will cache the resultant negative
JdeBP> responses for at most 24 hours (and so, given its popularity,
JdeBP> will probably ask a root server about "localhost.localdomain."
JdeBP> at least once per day).

JR> Read what I said.

I did.  What you said was wrong, for the reasons stated.

JR> The circumstances you describe are not those of a
JR> well behaved DNS setup.

Also wrong. The DNS setup described is behaving exactly as it should.  
You aren't thinking.  Think!  Think about what is and is not cached, and 
what back-end queries are sent where, when "localhost.localdomain." is 
looked up repeatedly.

More information about the bind-users mailing list