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I have come across the terms on several occasions however am unsure what they mean exactly.

PeanutsMonkey
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2 Answers2

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They refer to DNS GLUE records. Generally, they're used by the TLD domain name servers to respond to a query with both the name and IP address of the name server for the domain you ask for.

For example, if you ask the .com name server for "example.com", it will respond with a glue record along the line of "ns1.example.com 10.20.30.41"

It will actually come back as a set of separate records, so a query to the .com. name servers for the name server of example.com will look like this:

@     IN   SOA   ns1.example.com. hostmaster.example.com ([some timeout stuff, etc])
      IN   NS    ns1
ns1   IN   A     10.20.30.41
Hyppy
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  • Thanks. So does that mean that when a domain is queried it a DNS Glue record would only matter if the requested DNS is not able to provide a response. For example if I request the domain www.xyz.com, the request is initially sent to the ISPs' DNS servers which is turn go to the parent or top level domain name servers if it cannot return a response. – PeanutsMonkey Jul 22 '11 at 01:30
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    Sortof. Glue records are used when referring to a name server on the domain being queried for. If you ask for the name server of example.com, then being told "ns1.example.com" won't help much without an IP. If the authoritative name server for example.com was "ns1.opendns.com", then no glue record is strictly needed because you're not creating a circular reference. – Hyppy Jul 22 '11 at 01:36
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    @Peanuts The glue records are needed when the namerver for `domain.com` is `something.domain.com`. Without them, in order to find out the IP address of `something.domain.com` you'd have to ask `something.domain.com` which you couldn't do until you found out the IP address of `something.domain.com`. The glue records let other servers tell you what `something.domain.com`'s address is. – DerfK Jul 22 '11 at 01:37
  • @PeanutsMonkey: No. Re-read Hyppy's second sentence a few times. – womble Jul 22 '11 at 01:44
  • @Hyppy - So does that mean that glue records are only required from non-authoritative name servers? – PeanutsMonkey Jul 22 '11 at 01:57
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    @Peanuts They are required when your nameserver is inside its own domain instead of some other domain, and they come from the server that is authoritative for the next level up from your domain (ie the `.com` servers if your domain is `example.com`) See http://en.wikipedia.org/wiki/Domain_Name_System#Address_resolution_mechanism and continue to the next section on glue records. – DerfK Jul 22 '11 at 04:58
  • @DerfK - Thanks DerfK. Sorry if I am being a complete noob but do you mean that glue records are only relevant when I configuring a zone record for a name server – PeanutsMonkey Jul 22 '11 at 07:58
  • @Peanuts you configure them when you register your domain. When you tell the registrar that your nameserver is `ns1.domain.com`, the registrar should have a box somewhere nearby for you to put the IP address of `ns1.domain.com`. – DerfK Jul 22 '11 at 12:04
  • @DerfK - Right hence glue records are only for name server domains. Is that correct? – PeanutsMonkey Jul 22 '11 at 18:02
  • They're for the name servers on referred domains in which the name server resides as a member of the domain in question. – Hyppy Jul 23 '11 at 00:00
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@Hyppy's answer covers what glue records are.

The other bit of your question is mismatched glue. This is what you get when the glue records held by the parent zone don't match the NS and A records that are in your authoritative copy of the zone.

[technically those records in your own zone aren't glue - that term only refers to the non-authoritative data held by the parent zone].

Alnitak
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