Reverse DNS lookup

[Mark Damrose]

"Johnathan Leppert" <leppert at insight.rr.com> wrote in message
news:abjjak$dh0t$1 at isrv4.isc.org...
> > resolve to the same IP, and the reverse lookup only has to resolve to
one
> > of them.
>
> How is that? Is that via contacting the provider?

Most applications that check the reverse lookup are happy as long as it
resolves to something and that something resolves back to the same IP.  It
doesn't have to be the same as your name.

I contacted mine and they
> said since they own the IP addresses they had the right to decide the
> reverse DNS and would not change it or delegate it for me. They said I
> needed to request my own IP addresses from ARIN and buy them, then I would
> have the rights to the reverse DNS arpa files. But I looked over ARIN and
> they only support large requests of /24 and /19, and I don't need that
many
> (also the price is around $2400). I am currently only using four IP's, the
> problem is I am paying for each and every one so I should be able to
decide
> what those IP's resolve into, right?

No, you are paying for connectivity and support.  The IPs are there because
they are necessary for connectivity.  If your business need requires custom
reverse DNS and your provider won't do it, you should shop for a provider
that will.

>
> Is there any other way to change the reverse DNS? How is authority managed
> with reverse DNS, e.g. what is the query process like for nslookup
> xxx.xxx.xxx.xxx ?

Reverse DNS is delegated the same way the rest of the DNS name space is.
The root delegates in-addr.arpa. to ARIN.  ARIN delegates the number portion
of the name based on where they have allocated (to an ISP) or assigned (to
an end user) the IP addresses.  If an IP is allocated to an ISP, they decide
if they will delegate further or not.

>
> Also how would these new IP addresses be routable? I assume my ISP could
> route to them, but wouldn't I have to have several upstream providers to
> have some capability of global routing?

Not necessarily.  Your ISP should be able to list them in the global table
just like they do for their own.  Depending on your ISP's policy, you could
get more than one connection and use BGP yourself with their addresses.
What portable addresses allow you is to keep the same IP addresses if you
change providers.  This can be a big help if you have a large installation
and you would have to re-number in order to change ISPs.

>
> Thanks,
>
> Johnathan
>
>
> "Barry Margolin" <barmar at genuity.net> wrote in message
> news:abguq3$c8oc$1 at isrv4.isc.org...
> > In article <abgtqa$c2m7$1 at isrv4.isc.org>,
> > Johnathan Leppert <leppert at insight.rr.com> wrote:
> > >I am a T1 customer and whenever I do forward lookups on my domain, it
> yields
> > >the correct IP. However, when I do a reverse lookup based upon my IP it
> > >yields something like [myip].cust.provider.net. I don't currently run
my
> own
> > >nameservers, I use Public DNS. What type of bind configuration would
> allow
> > >me to provide reverse lookup services for my IP, so my IP wouldn't be
> > >resolved to that myip.cust.provider.net.? Does it have something to do
> with
> > >the in-addr.arpa config, because I see this often when I do reverse
> lookups
> > >by IP.
> >
> > You need your provider to customize your reverse DNS in one of two ways:
> >
> > 1) Change the reverse DNS entry to contain your custom hostname.
> >
> > 2) Delegate the reverse DNS for your address to some other nameservers,
> > e.g. ns1.granitecanyon.com and ns2.granitecanyon.com.  In this case, you
> > would then have to create this reverse domain on the GC nameservers,
just
> > as you did for your forward domain.
> >
> > But for most people this isn't necessary.  There's nothing wrong with
> > having two names (one in your domain, and the other in
cust.provider.net)
> > resolve to the same IP, and the reverse lookup only has to resolve to
one
> > of them.
> >
> > --
> > Barry Margolin, barmar at genuity.net
> > Genuity, Woburn, 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.
> >
>
>