inverse query:PTR RR or OPCODE=1 ?

Mark Andrews marka at
Thu Dec 3 03:03:03 UTC 2009

In message <4591889.164031259808158905.JavaMail.coremail at>, lipen
g967 writes:
> when I read the RFC1035, I noticed the opcode defination in the DNS
> message head . It said that when opcode = 1 the message did Inverse query.
> but in the packet  I capatured when I used nslookup to do inverse query
> ,the inverse query packet use the opcode = 0 and the question segment with
> RR TYPE PTR. Can someone explain this ?  Am I wrong about understanding the
> inverse query ? Thank a lot .

Nslookup does normal queries into the .ARPA namespace to do "reverse"

Inverse lookups were a concept that really only worked in the "dentist
surgery" senario (one server providing the entire DNS view).  Inverse
queries were deprecated years ago <>.


Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at

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