inverse query:PTR RR or OPCODE=1 ?
Joseph S D Yao
jsdy at tux.org
Thu Dec 3 02:58:41 UTC 2009
On Thu, Dec 03, 2009 at 10:42:38AM +0800, lipeng967 wrote:
> 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 .
>
Note that 6.4 (inverse queries) was optional, and read 3.5
(in-addr.arpa), which is about REVERSE (not inverse) DNS as it is used
today. With some additions and changes: the RFCs are living documents.
RFC 3425 obsolets inverse queries entirely:
The IQUERY method of performing inverse DNS lookups, specified in RFC
1035, has not been generally implemented and has usually been
operationally disabled where it has been implemented. Both reflect a
general view in the community that the concept was unwise and that
the widely-used alternate approach of using pointer (PTR) queries and
reverse-mapping records is preferable. Consequently, this document
deprecates the IQUERY operation, declaring it entirely obsolete.
This document updates RFC 1035.
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** Joe Yao jsdy at tux.org - Joseph S. D. Yao
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