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To begin, I am going to describe my organisation domain set up which may be common or uncommmon to everyone else, I am not sure since I am inexperienced -- but here goes:

We have the domain which is a registered domain i.e. you can do an nslookup on it. Incidentally, our organisation is physically separated at 2 different places hence our AD and other servers are actually set up under and like so

the third party web host machine at the IP of's A record is the machine for the authorative DNS (and web server), has its usual A and NS records, and records for the services which can be accessed externally, for example mail and VPN.

QUESTION (finally): I realized that a single A Record for, defined at, seems to be sufficient for the internet to find its way to our LAN server. But, is it really sufficient?

As some-service is a 4th-level domain (or is it 5th?), it surprises me when it even resolves as there are no entries for the intermediate levels. Why is this so? Or do I need to also set the NS for some-service at least?

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Intermediate entries aren't necessary; if there are skipped levels then the DNS server before the skipped ones must know how to get to the DNS server after the skipped ones.

For instance, say you have; The root servers know how to get to; could know how to get to, and recursion would skip altogether. It would then ask's NS for the d record.

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