Peculiar DNS problem

[Cuong]

Hi all,

I had a peculiar DNS problem a week ago and I am hoping someone could
explain to me why.

We are running Windows 2000 AD with integrate DNS. Everything works
just fine. A week a go I had a request to create a dns subdomain
called "myinet" the parent domain is called local.com. At the
parent domain, exists an alias record called "myinet", this alias is
pointing to an IIS server. I created the subdomain as requested with
even thinking about the alias with the same name. A couple of days
later, the request retracted and the subdomain was removed; there was
no record created under that subdomain yet.

A couple of hours later I received called that users were unable to
access the myinet, after troubleshooting, I found that the alias
"myinet" at the parent domain, local.com, was gone, I recreated the
alias and pointed to the proper server and voila the users can access
myinet, problem solved. When I retraced my steps and found out that
when I deleted the subdomain "myinet" under local.com, it also deleted
the alias with the same name.

Can someone please explain to me why this happened? I thought that
since DNS allowed me to create the subdomain with the same name as an
existing record, it must know how to distinguish between a subdomain
and an alias record. But I was Wrong. Is this how Windows DNS was
designed to work or is this a bug or something? Has anyone since this
problem with other DNS for Linux or Unix before?

It would be greatly appreciated if someone can clear up this question
for me. Thank you very much for your time and answer on this
questions.

Cuong

 

[Herb Martin]

just fine. A week a go I had a request to create a dns subdomain
called "myinet" the parent domain is called local.com. At the
parent domain, exists an alias record called "myinet", this alias is
pointing to an IIS server.

Then you cannot expect this to work correctly (AT the parent).

You must EITHER resolve this name at the parent OR you
may delegate it to another (child) DNS server set. You cannot
do both (at the same time.)

I created the subdomain as requested with
even thinking about the alias with the same name. A couple of days
later, the request retracted and the subdomain was removed; there was
no record created under that subdomain yet.

A couple of hours later I received called that users were unable to
access the myinet, after troubleshooting, I found that the alias
"myinet" at the parent domain, local.com, was gone, I recreated the
alias and pointed to the proper server and voila the users can access
myinet, problem solved. When I retraced my steps and found out that
when I deleted the subdomain "myinet" under local.com, it also deleted
the alias with the same name.

Sounds like a bug but not totally surprising as these records
should never have been created concurrently. Better would
have been an error for the additional but that is hard to do
(how does the DNS server know you don't really want this?)

Can someone please explain to me why this happened? I thought that
since DNS allowed me to create the subdomain with the same name as an
existing record, it must know how to distinguish between a subdomain
and an alias record. But I was Wrong. Is this how Windows DNS was
designed to work or is this a bug or something? Has anyone since this
problem with other DNS for Linux or Unix before?

Not many people have seen this because it doesn't make
sense to do this (as you learned) -- so most people who
are experience with DNS would never try it, and most
people who are unfamiliar with DNS would not be able
to recall or remember precisely what they did (you fall
somewhere in the middle since you were careful to remember
your steps.)

It would be greatly appreciated if someone can clear up this question
for me. Thank you very much for your time and answer on this
questions.

The best answer (really) is: "Don't do that". <grin>