DNS Glue Records

What are Glue Records

and what are they good for.

The main purpose

To explain Glue records by example, let us assume you own example.com.

And assuming, you only own that domain name, and you own 4 servers, 2 Nameservers, One web server, and one mail server.

Namserver 1   192.168.200.21
Namserver 2   192.168.200.22

Web Server    192.168.200.23
Mail Server    192.168.200.24

So you set your namserver host addresses to NS1.EXAMPLE.COM AND NS2.EXAMPLE.COM at the VeriSign .com registry

Now a resolver will call the .COM registry asking for example.com, and the registry will answer with the delegation, (Registry says: all info about example.com is at ns1.example.com), but now we are in trouble, we don't know who to ask for the address of NS1.EXAMPLE.COM, since NS1.EXAMPLE.COM is the nameserver that should itself provide the answer to this question (It's own address).

So, the resolution to this dead end is a Glue record at the .COM registry, where rather than answering (Ask NS1.EXAMPLE.COM), it would say, (ASK NS1.EXAMPLE.COM that is located at 192.168.200.21), now we really have no need to ask where the nameserver is, the registry told us and we know our way from this point on.

More on Glue records

Although the above is where Glue records are a necessity, the registry will also include the glue records to reduce needed queries if certain conditions are met, eliminating the need for a query on the A records of the namserver (And therefore saving time) The simple condition that needs to be met is.

the registry will provide a glue record if your domain name has the same TLD as the namserver Host name, so if your domain name is example.cc and your nameserver is ns1.myhosting.cc, the .cc registry will include the Glue records to speed things up for your visitors, saving them the need for 1 A record request.