Problem with hosting providers reverse DNS

Barry Margolin barmar at alum.mit.edu
Wed Aug 16 04:41:49 UTC 2006


In article <ebtaej$e3h$1 at sf1.isc.org>, andrewgroups at gmail.com wrote:

> When I run a reverse DNS search on our hosting provider,  this error
> "WARNING: Duplicate zone found ..."  appears randomly.  Some email
> server are blocking us and I suspect it is because they have something
> that is not well configured.  Can anyone figure out what the problem is
> and why this "Duplicate zone found" error is returned?

I'm not sure what it's talking about.  While the configuration of this 
zone is a little unusual, there doesn't seem to be anything technically 
wrong with it.  It's using RFC 2317 delegation, which is normally only 
used when delegating reverse DNS for a block smaller than /24, but in 
this case it's for a /24 block; but the technique doesn't really care 
what the block size is, and it should work fine for this.

Maybe dnsstuff doesn't really understand RFC 2317 delegation.  Perhaps 
you could write to them and ask what it's complaining about.

> 
> 
> Preparation:
> The  reverse DNS entry for an IP is found by reversing the IP, adding
> it to "in-addr.arpa", and looking up the PTR record.
> So, the reverse DNS entry for 216.133.255.56 is found by looking up the
> PTR record for
>  56.255.133.216.in-addr.arpa.
> All DNS requests start by asking the root servers, and they let us know
> what to do next.
> See How Reverse DNS Lookups Work for more information.
> 
> How I am searching:
> Asking i.root-servers.net for 56.255.133.216.in-addr.arpa PTR record:
>        i.root-servers.net says to go to figwort.arin.net. (zone:
> 216.in-addr.arpa.)
> Asking figwort.arin.net. for 56.255.133.216.in-addr.arpa PTR record:
>        figwort.arin.net [192.42.93.32] says to go to
> dns-01-002.root-dns.com. (zone: 255.133.216.in-addr.arpa.)
> Asking dns-01-002.root-dns.com. for 56.255.133.216.in-addr.arpa PTR
> record:
>        dns-01-002.root-dns.com [64.7.192.163] says to go to
> dns-01-001.root-dns.com. (zone: 255.133.216.in-addr.arpa.)
> 
> WARNING: Duplicate zone found (zone 255.133.216.in-addr.arpa. is
> repeated).  This can prevent the lookup from continuing
>          (BIND8 and BIND9 will cause a 'server failure' response).
> Although I will continue, be aware that
>          most DNS servers will not see your reverse DNS entry.
> 
> Asking dns-01-001.root-dns.com. for 56.255.133.216.in-addr.arpa PTR
> record:  Got CNAME referral to 56.0/24.255.133.216.in-addr.arpa. at
> server dns-01-001.root-dns.com. (zone 0/24.255.133.216.in-addr.arpa.)
> [from 64.7.192.162]
> Asking d.root-servers.net for 56.0/24.255.133.216.in-addr.arpa. PTR
> record:
>        d.root-servers.net [128.8.10.90] says to go to henna.ARIN.NET.
> (zone: 216.in-addr.arpa.)
> Asking henna.ARIN.NET. for 56.0/24.255.133.216.in-addr.arpa. PTR
> record:
>        henna.arin.net [192.26.92.32] says to go to
> dns-01-001.root-dns.com. (zone: 255.133.216.in-addr.arpa.)
> Asking dns-01-001.root-dns.com. for 56.0/24.255.133.216.in-addr.arpa.
> PTR record:  Reports NET-allocation-00025443.ix.sitestream.net. [from
> 64.7.192.162]
> 
> Answer:
> 216.133.255.56 PTR record: NET-allocation-00025443.ix.sitestream.net.
> [TTL 86400s] [A=None] *ERROR* There is no A record for
> NET-allocation-00025443.ix.sitestream.net. (may be negatively cached).
> 
> To see the reverse DNS traversal, to make sure that all DNS servers are
> reporting the correct results, you can Click Here.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***



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