in-addr.arpa domain

[Barry Margolin]

In article <3873ABDF.65300295 at mycomm.com>,
Milan Yagodich  <milan at mycomm.com> wrote:
>Hi-
>I don't understand how reverse lookups are managed/stored.  When you
>query any nameserver with an IP address, you get the domain name.  
>In my case, a query for mycomm.com turns up my ip address.
>mycomm.com      internet address = 205.252.165.66        
>
>and a reverse inquiry, yields my isp (mycomm.com is a virtual domain
>under websp.com)
>66.165.252.205.in-addr.arpa     name = websp.websp.com   
>
>Does the in-addr.arpa domain reside at the rootservers?

Yes.  The 252.205.in-addr.arpa zone is delegated from the root servers to
CAIS's nameservers.  They then delegated 165.252.205.in-addr.arpa to
WEBSP's nameservers.

>The basis for my question is this.  I am going to move mycomm.com from
>its virtual host to my own machine when the DSL gets hooked up.  I plan
>on running my own nameservers.
>
>I did a reverse lookup on my new block of addresses and got
>xxx.xxx.xxx.xxx-sdsl.line.cais.net.  If my nameservers have the correct
>A and PTR records for mycomm.com, which domain name will get returned
>when I do a reverse query on my new address?

Unless you can convince CAIS to change the PTR record or delegate to your
nameserver, you'll get the cais.net name.  No one on the Internet knows
that they should ask your nameserver.

>How does the in-addr.arpa domain know which is the correct PTR record?

They just work their way down the hierarchy, following nameserver
delegations, just like any other domain.

-- 
Barry Margolin, barmar at bbnplanet.com
GTE Internetworking, Powered by BBN, Burlington, MA
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