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I kind of know why glue records are needed (cyclic dependencies), but when are they needed? Are they only needed when setting a domain's nameservers to my own machine on the internet - like "" ??

Is there any need / point in making glue records when using external / hosting provider's nameservers?

Beginner question sorry (T_T)

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3 Answers 3

up vote 11 down vote accepted

You only need glue records when the hostname for your nameserver is part of the same domain as it's trying to serve.

Glue records are published in the parent zone. Hence if the operator of wanted to have nameservers named and then the .com domain would need something like:     IN NS
                 IN NS IN A IN A

(example subnets taken from RFC 5737).

The child zone would usually have the same A records in it (even if only for consistency), but when they're in the child zone they're not technically glue records any more.

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I guess this entry from Wikipedia should answer that pretty well:

Circular dependencies and glue records

Name servers in delegations appear listed by name, rather than by IP address. This means that a resolving name server must issue another DNS request to find out the IP address of the server to which it has been referred. Since this can introduce a circular dependency if the nameserver referred to is under the domain for which it is authoritative, it is occasionally necessary for the nameserver providing the delegation to also provide the IP address of the next nameserver. This record is called a glue record.

For example, assume that the sub-domain contains further sub-domains (such as and that the authoritative name server for these lives at A computer trying to resolve will thus first have to resolve Since ns1 is also under the subdomain, resolving requires resolving which is exactly the circular dependency mentioned above. The dependency is broken by the glue record in the nameserver of that provides the IP address of directly to the requestor, enabling it to bootstrap the process by figuring out where is located.

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not upvoting someone just for quoting Wikipedia... –  Alnitak Apr 26 '10 at 7:23

In regard to the when, they are needed when you first introduce a new nameserver to the Internet. Once that nameserver has a glue record it can be found by name.

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