[PLUG] Victor is trying to understand DNS

Bill Barry bill at billbarry.org
Sun Oct 14 08:41:08 UTC 2007


On 10/14/07, Victor Soich <vsoich at gmail.com> wrote:
> On 10/14/07, Bill Barry <bill at billbarry.org> wrote:
> >
> > The answer to your question is hidden in this set of riddles.
> >
> > What does a nameserver do?
>
> A nameserver tells a client what name and domaian of a host is
> associated with what IP address.
>

This is reversed. You send a nameserver a name and it returns an IP address.

>
> When do you need one?
>
> You need one when you want a host to be available to the internet clients.
>
Not exactly. If the internet client knows the ip address of the host,
it  does not need a nameserver.  You need the nameserver if the client
only knows the host's name. The client needs the ip address in order
to be able to contact the host, so the client gives the host name to
the nameserver and gets back the ip address it needs.

>
> Does dyndns.org
> > qualify as a nameserver?
>
> I suppose it does.  It tells a client what host is associated with
> which dynamic ip address.
>
dyndns.org does have nameservers.  Nameservers take host names and
return ip addresses.

> >
> > What is a static IP?
>
> It is an IP address that doesn't change.
>
>
>  If I gave you two IP addresses and one was
> > static and the other dynamic could you tell me which one was which?
>
> No, I don't think I could.
>
>
> > If not then what does it matter, and more importantly when does it
> > matter?
>
> As far as what does it matter goes, I guess it doesn't matter.  I
> guess I can set up a DNS primary nameserver using my dynamically
> allocated IP address from comcast.  But what about my secondary
> nameserver.  It seems that one is suppose to set up a seconary
> nameserver if your primary one goes done, but then how does dyndns
> find the secondary if the primary goes done, and the primary name
> server host is associated with my dynamically allocated IP address.
>

Primary nameservers and secondary nameservers are both nameservers.
They provide redundancy. If one is busy or not working the other one
does the job.
Both nameservers have to be updated with the dynamic ip address.

 There is a hierarchy of nameservers that starts out at the top with
the root nameservers.  If the name/ip address is not cached locally
the query  goes to the root nameserver.   (See
http://en.wikipedia.org/wiki/Root_nameserver for a more complete
explanation.)

>
> As far as when does it matter goes, I guess it matters when comcast
> changes my IP address, which I hear is rare, but it does happen, but
> then I think my dyndns configuration file is suppose to update
> dyndns.org.

That is correct.

( I'll be asking questions about the dyndns configuration
> file too, when I figure out how to articulate those questions.  )
>
>
> Did I answer your riddles correctly?  I'm not being flippant, and I'm
> not quite sure if my answers were right.  I'm being earnest and hope
> for more feedback.
>


> Thank you for your consideration.
>
> Sincerely,
> Victor Soich
> _______________________________________________


I think I have not fully answered your questions. Which answers need
more explanation?

Bill



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