Reverse lookup on mail routers fail

[phn at icke-reklam.ipsec.nu]

Thomas Anderson <whatisthematrix at mail.dk> wrote:
> Hi all

> I hope someone will be able to help a DNS newbie. My problem is somewhat
> generic so I will explain it in generic terms.

> Suppose you I had a company that had bought a class B subnet. The company
> buys the rights to company.com and sets up two DNS servers to be
> authoritative for company.com. It then sets up two mail routers and add
> their IP addresses (lets just say the one with the lowest preferences has an
> IP of 1.2.3.4) as MX records in their DNS servers. The DNS servers has a
> reverse lookup zone for company.com and has PTR entries for all its servers
> including the mail routers. The problem is this:

> Whenever I query the company's own DNS servers for the address of
> company.com's mail routers:

> nslookup -type=mx company.com <own DNS server>

> it returns the entries specified correctly. When I try to query any internet
> DNS server I can think of, it also correctly returns a correct
> (non-authoritative) answer.

> If i try to do a reverse lookup query on my mailrouters on my own DNS
> servers it also works:

> nslookup -type=ptr <mailserver's IP> <own DNS server>

> I returns with the hostnames of my mailrouters. However, the same query
> fails against any public Internet DNS

> internetdnsserver.com can't find 4.3.2.1.in-addr.arpa.: Non-existent domain

> So it seems thay my DNS servers are operating correctly (since they are
> responding correctly to the queries when queried directly), but the public
> Internet DNS servers don't know where to refer any queries for
> 4.3.2.1.in-addr.arpa. My question is now this:

> Where am I supposed to "register" the IP addresses of my mail routers to
> allow referall to my 4.3.2.1.in-addr.arpa address?

Usually at the same place where you got the ip-address.

Tell us the ip-range and we will tell you!







-- 
Peter Håkanson         
        IPSec  Sverige      ( At Gothenburg Riverside )
           Sorry about my e-mail address, but i'm trying to keep spam out,
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