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Explanation of a Glue Record

A glue record in simplest terms is an IP address that is "glued" to a specific domain or subdomain in the registry. Glue records are most commonly needed for users that are trying to use name server addresses that are subdomains of the domain itself. To explain a little further:

John has a domain registered named domain.co.uk. John wants to set up his own name servers (DNS) using the addresses ns1.domain.co.uk and ns2.domain.co.uk. The problem with this is that because of the way that DNS works, every time someone tries to access domain.co.uk, they will have to check with one of the subdomains (ns1.domain.co.uk or ns2.domain.co.uk) for the address which are both "under" the domain. Since you can't get to a subdomain before getting to the domain, and the domain is what we are looking for in the first place, we seem to be stuck. Let's personify the process for finding the correct address for a domain in the DNS lookup process:

Q: "I am trying to find domain.co.uk. What is the IP address for the website domain.co.uk?"
A: "I do not have the address. Check the name server for domain.co.uk. You will find the address there."
Q: "Okay. What is the name server for domain.co.uk?"
A: "ns1.domain.co.uk"
Q: "Okay. What is the address for ns1.domain.co.uk so I can check there?"
A: "I do not have the address. ns1.domain.co.uk is a subdomain of domain.co.uk. So check the name server for domain.co.uk."
Q: "Okay.... What is the name server for domain.co.uk?"
A: "ns1.domain.co.uk"
Q: "You just said that. So you know the name of the name server but don't have the address?"
A: "Yes, only the name server has the address of the name server!"
Q: "So if only the name server knows the address for the name server, how am I supposed to get the address?!"

The solution to this is to set up a glue record. A glue record will glue the IP address to the domain/subdomain so that the process is a bit more like:

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

This time the name came with an address since they were "glued" together! Now that's helpful!

This process may seem very technical but setting up a glue record in the 1&1 Control Panel is actually quite easy and may have already happened without you even knowing it. Any time a subdomain is created with "ns" at the beginning, a glue record is automatically created for this subdomain.

For additional information, you may want to reference: