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Hello I've a question because i'm not sure about something. When I perform whois on domain.com I get something like :

Domain servers in listed order :
ns1.domain.com
ns2.domain.com

The IP from ns1.domain.com is 'hard coded' in the registrar. My question is when I do a host on ns1.domain.com, I retrieve the IP from registrar or from my DNS server ?

Thanks, I hope it's not too confused.

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3 Answers 3

Your question isn't really about registrars, it's about the DNS system and how it works.

DNS can be quite difficult to understand when you start getting into the pointy end of it (GLUE records, etc).

When you purchase a domain, and you enter your nameservers, whatever you enter are created as what's called "GLUE" records. These records are, in laymans terms, "hard coded" in the registrar, as you have said (well, they're not hard coded, but that's the best way to describe it).

And the reason for this is, that when you go to www.example.com, and the nameserver is ns1.example.com, how the hell does it know how to find the nameserver, when the nameserver has the same damn IP domain as the website? The GLUE records, thats how.

When you look up ns1.domain.com, ns1 is a subdomain of domain.com, so it looks at the domain.com DNS to find out which IP address to map to (by going back to the GLUE record that the registrar for domain.com has listed).

In short, ALL records you are looking at come from a DNS somewhere on the internet. Maybe it's a root server, maybe it's an authoritive server, but it's still a DNS server, not a registrar.

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Ok so ns1 & ns2 in the list ( from whois ) are just 'decorative objects', I mean the important thing is the IP behind ns1 & ns2. Thanks a lot : how the hell does it know how to find the nameserver, when the nameserver has the same damn IP domain as the website? It's exactly what I didn't understand this morning ! –  Eno Jan 4 '10 at 21:16
    
It knows how to find them because of the 'glue' record that the registrar submits to the TLD. As you said, it's kind of a "hard coded" record that exists at the next level up. So a glue record for 'ns1.example.com' exists at the DNS server for 'example.com' - and the 'example.com' record exists at the 'com' level, and it travels backwards from there –  Mark Henderson Jan 4 '10 at 21:45
    
Bad explanation: most registries will NOT publish (or even ask) glue records unless they are necessary (because they are in the domain they serve). –  bortzmeyer Jan 11 '10 at 15:45
    
Yes, but his question was about what to do when your NS is within your own domain, so the explanation still stands valid –  Mark Henderson Jan 11 '10 at 20:36

My answer to this other DNS question may prove enlightening for you as to how DNS works.

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"host" uses only DNS. The TLDs get their basic config from the registry, so in theory they should be the same, but DNS is the actual authority on what is true for applications.

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