What is a Glue Record?

A glue record is an A or AAAA record that lives in the parent zone and supplies the IP address of a nameserver whose hostname is inside the domain that nameserver is responsible for. Rather than living in your own zone file, it sits one level up at the registry so resolvers can find the nameserver before they ever talk to it.

The classic example is a domain like example.com served by ns1.example.com and ns2.example.com. The names of the nameservers are themselves inside example.com, and that is precisely the situation glue exists to handle.

To understand why glue is needed, follow what a resolver tries to do when a domain uses in-zone nameservers:

1. The resolver wants the address for example.com, so it asks the .com servers who is authoritative for that domain.
2. The .com servers answer with the NS records, which say to ask ns1.example.com.
3. To query ns1.example.com, the resolver needs its IP address, so it tries to resolve ns1.example.com.
4. But ns1.example.com lives inside example.com, whose only nameserver is the one the resolver is trying to reach. It is stuck in a loop.

The delegation points at a nameserver that can only be found by asking that same nameserver. Nothing can break the cycle from within DNS alone.

Glue records break the loop by attaching the nameserver's IP address directly to the delegation in the parent zone. When the .com servers return the NS records for example.com, they also include the glue, an extra A record stating that ns1.example.com is at a specific address.

Now the resolver has everything it needs in one step: it knows which nameserver to ask and exactly where to reach it, with no separate lookup required. The cycle is broken because the parent zone supplies the bootstrap address out of band.

Glue is only required in specific situations:

• In-zone nameservers — whenever a domain is served by nameservers whose hostnames are inside that same domain, glue is mandatory.
• Vanity or custom nameservers — hosting providers and large operators often offer branded nameservers like ns1.yourbrand.com, which require glue at the registry for yourbrand.com.

If your nameservers live on a different domain, for example example.com using ns1.cloudprovider.net, glue is not needed. The provider's own domain already has normal address records that any resolver can look up without circularity.

You normally create glue through your registrar by registering each nameserver hostname together with its IP address, an action often labelled a host record or registering a nameserver. Because glue lives in the parent zone, you cannot fix it from inside your own DNS provider.

Stale or missing glue is a common cause of intermittent resolution failures, especially after changing a nameserver's IP address without updating the registry. Keeping an eye on your delegation matters, and ZoneWatcher alerts you the moment your nameserver configuration changes so a broken delegation does not quietly take your domain offline.