[oclug] What is the IP addres of a domain?

[OddSox]

On Oct 24, 2007, at 10:42 AM, Andy Civil wrote:

> Stephen Gregory wrote:
>> On Fri, Oct 19, 2007 at 12:37:42PM -0400, Andy Civil wrote:
>>> What is the IP addres of a domain? Is it:
>>>
>>> a. Whatever the name server, specified in the DNS record, says it  
>>> is.
>>> b. Whatever the domain's A record says it is.
>> Items a and b are the same thing.
>
> Is that "c" then? The barrier to my understanding is that the  
> domain registrar "knows" which name servers are responsible,  
> because I've told them, but it's up to the hosting company to  
> define which host (and hence which IP address) to send browsers to.  
> The domain registrar seems to know what the IP address is, to  
> supply the "A" record(s). How? I didn't tell them, and they don't  
> define it.

Your domain registrar does not actually know what the address is -  
they have to look it up like anybody else.

The following is probably really oversimplified but...

The only thing the domain registrar needs to know is the domain name  
and the 'name server' responsible for that domain. This information  
gets stored in the 'root' domain server. When a browser looks for  
your domain name, it checks with the 'root' server to find the 'name  
server' responsible for your domain. Then it asks that 'name server'  
for the appropriate IP address based on the A record stored on the  
'name server'.

Try http://en.wikipedia.org/wiki/Domain_name_system for a more  
detailed explanation, with charts and diagrams but no 8x10 glossy  
photos...

Fred