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Since glue records already provide the IPs of each NameServer, why are A records pointing to the IP of the NameServer still required on the server itself?

For example :

Q: "I am trying to find domain.com. What is the IP address for the website domain.com?"
A: "I do not have the address. Check the name server for domain.com. You will find the IP address there."
Q: "Okay. What is the name server for domain.com?"
A: "ns1.domain.com(127.0.0.1)"

The parent zone (com) already provides the IP of that nameserver, I can't see why an A record is required.

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2 Answers 2

up vote 5 down vote accepted

Glue records are not authoritative, and therefore should not be accepted as an answer by a resolver. They exist only to bootstrap the resolution process, avoiding a loop when the nameserver is in the same zone that you are trying to resolve.

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Oh I thought a glue record already acts like an A record. What would happen if there's no A records on the server itself? –  user75228 Apr 5 '11 at 9:42
    
generally only your domain will have working nameservers... if you host other domains that are not in the same tld as your nameservers domain then they likely wont be able to resolve the actual nameserver IP's, GLUE is only a helper not authoritave dns –  anthonysomerset Apr 5 '11 at 9:45
    
@user75228 BIND won't load a zone whose configured nameservers are missing A records: Apr 5 11:58:11 localhost named[9424]: zone test/IN: NS 'ns.test' has no address records (A or AAAA) Apr 5 11:58:11 localhost named[9424]: zone test/IN: not loaded due to errors. –  Cakemox Apr 5 '11 at 9:58

If you didn't have an A record for your nameserver, how would another nameserver resolve your host?

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