Proper response of reverse lookup private IPs

[Adam Lang]

My main DNS is hosted by my provider, PSINet.

I have a BIND server setup for strictly caching (10.10.10.6).
Currently private IPs are not listed in the DNS.

I typed in this command at a computer that is using 10.10.10.6 for its DNS
lookups.
 dig 51.10.10.10.in-addr.arpa PTR

I get the response (after some time goes by) of
; <<>> DiG 8.2 <<>> 51.10.10.10.in-addr.arpa PTR
;; res options: init recurs defnam dnsrch
;; res_nsend to server default -- 10.10.10.6: Connection timed out

Is that normal and if so, should it be quicker than 15+ seconds?

Adam Lang
Systems Engineer
Rutgers Casualty Insurance Company
http://www.rutgersinsurance.com