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Re: How does networking (communication) work when in the cloud



fixed

Hi Nathan -

On Fri, 1 Aug 2014 17:52:02 -0600, Nathan Andelin <nandelin@xxxxxxxxx>
wrote:

Here's a link to an article that explains subdomains and shows how to
add them by adding DNS host (A) records:

http://support.godaddy.com/help/article/4080/managing-a-domain-names-subdomains

GoDaddy is using the term subdomain incorrectly also, which doesn't
particularly surprise me. (If you think I have a low opinion of
GoDaddy, you are correct.)

I think Charles was a bit misleading when talking about subdomains and
name servers. Quite often the DNS for subdomains is on the same name
servers as the DNS for the domain. But it doesn't have to be. He is
correct that a true subdomain must have defined name servers, even if
they are the same name servers as those of the domain.

The very top of the DNS system is the root, which has a bunch of name
servers scattered around the world. These name servers point to the
name servers for the top-level domains, such com and net.

Top-level domain com has a bunch of name servers which point to the
name servers of the various .com domains.

Each of those domains (if it is an active domain) has one or more name
servers which:
1. Point to the name servers of any *subdomains*.
2. Have A, CNAME, and MX records for the *hosts* in the domain.

Any subdomain (if it is an active subdomain) has one or more name
servers which:
1. Point to the name servers of any next level *subdomains*.
2. Have A, CNAME, and MX records for the *hosts* in the subdomain.

A subdomain might be pingable, but that's only if there is a null host
resource record.

That null host requirement applies to the domain also. I have a
number of domains, the main one of which is kensims.net. If you try
to ping kensims.net, you won't get anywhere because I didn't define a
null host A or CNAME record for the domain.

None of my domains have subdomains so unfortunately I can't provide a
real world example from personal experience.

If you really want to understand how DNS works, I recommend something
like "DNS and BIND" published by O'Reilly. Even though I use a paid
name server service, I bought the book just to learn more about DNS.

Ken
Opinions expressed are my own and do not necessarily represent the views
of my employer or anyone in their right mind.





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