Reverse mapping question

[shh at tamu.edu]

Thanks for the reply, I think I understand now... but I have some more questions,
if you don't mind.  In a forward lookup (ie, resolving name -> IP address), would
it matter if they had delegated the reverse block to me?  My understanding is that
a forward lookup would work like this:

Let's say someone wants to connect to www.domain.com.  Their DNS is queried, and
since it has no listings for domain.com, it queries one of the root servers to find
out who controls the "com." top level domains.  It then queries that server to see
who controls the domain.com zone.  And finally, it queries that nameserver (who
incidently controls the domain.com zone) and receives an IP address.  Now the user
connects to that IP address.  The root server knows which name server is in charge
of the domain.com zone because that's how it was registered with Network
Solutions.  Does this sound correct?

While I'm at it, let me test my understanding of reverse mappings.  Say my IP
address is 1.2.3.4.  If someone wanted to find out the hostname for that IP
address, their DNS would query in-addr.arpa, to find out the name server who is in
charge of the "4" zone.  It would then query the "4" name server to see who was in
charge of the "3" zone, and so on.  Now let's say that my ISP was given control of
the 1.2.3 network (by whoever does that).  In order to find out which name server
has control over host 4 (assuming class C network), then it would have to specify
my name server has having control that ip address.  And unless they delegate that
to me, they will still be in control, and the name will resolve to something like
host.ISP.com.  Does this sound correct?

Is reverse mapping really necessary?  Would it be feasible for me to host a domain,
without having the IP address delegated to my name server's control?

Thanks for you help,
Steve Hodgson

Barry Margolin wrote:

> In article <37B4AA2F.43A17F0C at tamu.edu>, shh at tamu.edu <shh at tamu.edu> wrote:
> >Well, I've been reading all that I can find on running a DNS on Linux.
> >I'm still a little confused about the reverse mapping.  It seems that
> >somehow, my ISP has to tell in-addr.arpa (I think) that they are no
> >longer in charge of DNS for my IP address.  Is that correct?
>
> No.  Your ISP is in charge of their block of addresses, and if they
> delegate part of that to you they tell everyone who asks them.  DNS is
> hierarchical: the servers for in-addr.arpa tell everyone where the servers
> for z.in-addr.arpa are, the servers for z.in-addr.arpa tell everyone where
> the servers for y.z.in-addr.arpa are, the servers for y.z.in-addr.arpa tell
> everyone where the servers for x.y.z.in-addr.arpa are, and so on.
>
> >I guess my question is really this.  In the near future, I'd like to
> >host my own domain, and provide DNS services for it.  Does my ISP have
> >to do anything in order for me to use my IP address for such a purpose?
>
> They have to delegate the reverse block to you.  If they've assigned a
> block smaller than /24 (a class C) then they should use the technique in
> RFC 2317.
>
> --
> Barry Margolin, barmar at bbnplanet.com
> GTE Internetworking, Powered by BBN, Burlington, MA
> *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
> Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.