Newbie DNS question

[Barry Margolin]

In article <d0am5t$1gig$1 at sf1.isc.org>, matthewpascucci at yahoo.com 
wrote:

> I have a few DNS questions that I hope someone can explain to me. I
> have been looking on the web but can't really find the answers I'm
> looking for.
> 
> 1. When you have an ISP host your DNS what does this really mean??? Are
> they hosting all the local computers that are in your domain????

No, they're just running the servers that provide name lookup services 
for your domain.

> 
> 2. What is the real purpose of an external DNS server???

Fault-tolerance, so that people can look up names in your domain even 
when your Internet connection is down.

> 
> 3. When you do a lookup of some domain names you get NS servers that
> are local to that orgization, does this mean that they are hosting
> there own extenal DNS????

Usually, although it's possible that they have out-sourced the 
operations and they've had the out-sourcing company use names in their 
domain.

> 4. I have a friend who registered a domain name so he could run a
> website. He wants to run mail now for the domain. When we did a lookup
> for the domain a 0 mx mail.mydomain.com is already present. How does
> this work if he doesn't have a mail server setup yet and no machine
> named "mail" in his domain.

It doesn't work.  Someone apparently put that in there just as a 
placeholder.  If he wants to run mail, he'll need to update the DNS to 
point to the actual name of his mail server.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***