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RE: lame delegations

  • From: Greg A. Woods
  • Date: Fri Aug 18 17:07:04 2000

[ On Friday, August 18, 2000 at 12:54:30 (-0700), Karyn Ulriksen wrote: ]
> Subject: RE: lame delegations
> What about when you're setting up ARPA entries referring to CIDR
> allocations?
> as in ...
>    86400  IN   CNAME    1.0/
> Somethings got to give there.  I know that you could say well, just put the
> hostname instead of the target listed above, but the above is often used to
> delegate ARPA for subnets to downstreams...

That's not an issue.  What RFC-1912 omits from its descriription is the
fact that CNAME processing may occur during the retrieval of a PTR, as
clarified in RFC-2181:

10.2. PTR records

   Confusion about canonical names has lead to a belief that a PTR
   record should have exactly one RR in its RRSet.  This is incorrect,
   the relevant section of RFC1034 (section 3.6.2) indicates that the
   value of a PTR record should be a canonical name.  That is, it should
   not be an alias.  There is no implication in that section that only
   one PTR record is permitted for a name.  No such restriction should
   be inferred.

   Note that while the value of a PTR record must not be an alias, there
   is no requirement that the process of resolving a PTR record not
   encounter any aliases.  The label that is being looked up for a PTR
   value might have a CNAME record.  That is, it might be an alias.  The
   value of that CNAME RR, if not another alias, which it should not be,
   will give the location where the PTR record is found.  That record
   gives the result of the PTR type lookup.  This final result, the
   value of the PTR RR, is the label which must not be an alias.

							Greg A. Woods

+1 416 218-0098      VE3TCP      <[email protected]>      <robohack!woods>
Planix, Inc. <[email protected]>; Secrets of the Weird <[email protected]>