====== Glue records (definition) ======

A **glue record** is simply the association of a [[.:host-name|hostname]] ([[.:name-server|nameserver]], or DNS) with an IP address at the registry. 

In order for a nameserver to "work," it needs to be able to be found first. This is done by creating a glue record.


===== When to use glue records =====

Glue records are needed when you want to set a domain's [[.:name-server|nameservers]] to a [[.:host-name|hostname]] that is a [[.:#subdomain|subdomain]] of the domain itself.

In such a scenario, if you do not provide the registry with glue records, other nameservers trying to look up the [[.:ip-address|IP address]] of ''example.com'' would ask the ''.com'' nameservers for a referral, thus encountering the following catch-22:

<block>
**Your browser:** \\
Hi! I need the IP address of ''example.com''. What is it? \\

**.com nameserver:** \\
I don't know, but you can ask its nameserver. It was ''ns1.example.com'' [[:en/domains/management/zone/ttl|the last time I checked]]. \\

**Your browser:** \\
Thanks! Okay, in order to send a query to ''ns1.example.com'', I need its IP address. What is it? \\

**.com nameserver:** \\
I don't know, but you can ask its parent ''example.com''. \\

**Your browser:** \\
:-(

</block>

If you set a glue record at the registry, the DNS lookup would go more like this:

<block>

[...] \\
**Your browser:** \\
Thanks! Okay, in order to send a query to ''ns1.example.com'', I need its IP address. Do you have it? \\

**.com nameserver:** \\
Yes, it was ''192.0.43.11'' [[:en/domains/management/zone/ttl|the last time I checked]]. \\

**Your browser:** \\
:-D
</block>


====== Creating a glue record ======

//See [[:en/domains/management/change-glue]]// ->

Glue records are created at the registrar of the domain name. 

If your domain name is registered with Gandi, there are two different ways of creating a glue record, depending on the TLD. 

The most common TLDs will allow you to create your glue record directly from your domain's [[https://www.gandi.net/admin/domain|control panel]]; just click on the "Glue record management" link (in the lower right-hand corner in the "Name servers" section). If you do not see the Glue record management link, please [[http://en.gandi.net/support/contact/|contact Gandi support]] for assistance.



===== Examples of valid glue records =====
Gandi's default nameservers, which you have come to know and love by now, have the following glue records:

  a.dns.gandi.net 217.70.179.40
  b.dns.gandi.net 217.70.184.40
  c.dns.gandi.net 217.70.182.20

In this example, the host name ''a.dns.gandi.net'' is registered at Verisign (the registry for .net) as pointing to the machine ''217.70.179.40''. 

Therefore, when requests are made by a domain name that use ''a.dns.gandi.net'' as a nameserver, ''a.dns.gandi.net'' will send the request to the DNS server hosted on the machine called ''217.70.179.40'', which will tell it what to do.


===== Error messages =====
If you try and apply nameservers to your domain on Gandi's DNS update interface and get the following message (in this example, let's say I want to use ''boom.whack-a-mole.eu''): 

  The following error occurred while changing the DNS of your 
  domain: boom.whack-a-mole.eu: The domain name used as DNS server does not exist.

This means that no glue records exist for nameserver ''boom.whack-a-mole.eu'' at the registry. In other words, you need to go to the registrar of ''whack-a-mole.eu'' (Gandi) and first create a glue record for ''boom.whack-a-mole.eu''. Otherwise, there is no way that the registry will know what server will respond to that name.


If the glue record is valid, and the DNS does not respond, then it is a server-side issue; the registrar simply tells the registry what IP address corresponds to the given host name. In this case, the administrator of the DNS server needs to verify the configuration of the server. It is useless to contact the registrar in this case, as they do not have access to the actual server. If you are not running the DNS server yourself, you can perform a [[http://www.gandi.net/whois|whois lookup]] of the IP address itself to see who to contact.

===== See also =====
  * [[:en/domains/management/change-glue]]

===== External resources =====
  * Zytrax.com: [[http://www.zytrax.com/books/dns/ch8/ns.html|Name Server Record (NS)]] (advanced)