Multiple PTR reverse lookup problem (BIND9 resolver broken?)

[Barry Margolin]

In article <a7oaqj$mmh at pub3.rc.vix.com>,
Simon Waters  <Simon at wretched.demon.co.uk> wrote:
>
>David wrote:
>> Finally, should I inform my ISP that the fine experts here do not
>> recommend multiple PTR records for the same address due to the
>> pontential problems and complications to proper reverse DNS
>> resolution?  It seems to me a very unnecessary and improper way to
>> handle a reverse zone (what is so hard about deleting the 'default'
>> entry after adding a new PTR anyway?)  Please let me know if more info
>> is needed, thanks.
>
>It's been discussed in depth before see the archives. The most
>you can say is some of the experts here think it is unnecessary
>waste of bandwidth, but the RFC's are unambigous 2181 states
>multiple PTR's are allowed.

Multiple PTRs are allowed, but this "default" entry sounds fishy.  Any name
returned in a reverse lookup should resolve to the original IP address.  If
all their PTR records have this same default entry, it doesn't seem likely
that it will resolve to his server's address -- it would have to have an A
record for every address the ISP uses.

I've heard of companies trying to use wildcard PTR records, e.g.

*.xx.xx.xx.in-addr.arpa. PTR generic-host.company.com.

This is invalid for the same reason: generic-host.company.com doesn't
generally have all 256 possible addresses.

-- 
Barry Margolin, barmar at genuity.net
Genuity, Woburn, MA
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