Subject: Re: name server problem NetBSD-current/stunos
To: None <greywolf@defender.VAS.viewlogic.com, J.D.Coleman@newcastle.ac.uk>
From: Don Lewis <email@example.com>
Date: 04/29/1996 21:10:46
On Apr 29, 11:22am, greywolf@defender.VAS.viewlogic.com wrote:
} Subject: Re: name server problem NetBSD-current/stunos
} NOTE: I understand the phrase "inverse query" to mean "given IP address
} A.B.C.D, query the server D.C.B.A.in-addr.arpa and return a name". If
} this is an incorrect assumption, kindly disregard this letter.
This is what RFC 1035 says about inverse queries:
6.4. Inverse queries (Optional)
Inverse queries are an optional part of the DNS. Name servers are not
required to support any form of inverse queries. If a name server
receives an inverse query that it does not support, it returns an error
response with the "Not Implemented" error set in the header. While
inverse query support is optional, all name servers must be at least
able to return the error response.
6.4.1. The contents of inverse queries and responses Inverse
queries reverse the mappings performed by standard query operations;
while a standard query maps a domain name to a resource, an inverse
query maps a resource to a domain name. For example, a standard query
might bind a domain name to a host address; the corresponding inverse
query binds the host address to a domain name.
Inverse queries take the form of a single RR in the answer section of
the message, with an empty question section. The owner name of the
query RR and its TTL are not significant. The response carries
questions in the question section which identify all names possessing
the query RR WHICH THE NAME SERVER KNOWS. Since no name server knows
about all of the domain name space, the response can never be assumed to
be complete. Thus inverse queries are primarily useful for database
management and debugging activities. Inverse queries are NOT an
acceptable method of mapping host addresses to host names; use the IN-
ADDR.ARPA domain instead.