Reverse Delegation

phn at phn at
Thu Nov 4 08:09:28 UTC 2004

Jim McAtee <jmcatee at> wrote:
> We just started using a new ISP for connectivity at our offices.  They're 
> a reseller of another, national ISP.

> I'm trying to get them to set up delegation of reverse DNS for our 
> network.  I believe the reseller has some access to the larger ISPs DNS 
> systems so that they can set up PTR records or CNAMEs in the 
> zones for their customers.  I'm not sure that they can create NS records 
> to delegate subzones, however.

> Instead of them doing a fairly standard RFC 2317 delegation, as we've 
> always done with our providers

> 0-26    IN NS
>         IN NS
> 0       IN CNAME
> 1       IN CNAME
> 2       IN CNAME
> etc.

> would the following, without creating a delegated subzone, work just as 
> well, or are there potential problems?

> 0       IN CNAME
> 1       IN CNAME
> 2       IN CNAME
> etc.

This last method will work well, in addition you will get away 
with only one zonefile ( 

In addition to your normal SOA NS MX & A records add PTR records looking like :

0-officenet   IN  PTR   <name-of-host-using-1st-ip>
1-officenet   IN  PTR   <name-of-host-using-2nd-ip>

repeat until done.

The nice thing is that grouping A and PTR records together reduces the 
risk of errors.

Peter Håkanson         
        IPSec  Sverige      ( At Gothenburg Riverside )
           Sorry about my e-mail address, but i'm trying to keep spam out,
	   remove "icke-reklam" if you feel for mailing me. Thanx.

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