Glue records

Glue records are special entries in the DNS stored in the parent domain's zone that supply the IP address of a nameserver located inside the domain that nameserver serves. Their job is to break a circular dependency that would otherwise make such a domain impossible to resolve.

The problem glue records solve

Imagine the domain mycompany.com, whose nameserver is ns1.mycompany.com. To learn that server's IP address, a resolver would have to query the DNS of mycompany.com — but to do that, it needs the very address ns1.mycompany.com. A chicken-and-egg loop forms.

The solution is to place an extra A or AAAA record alongside the NS record in the parent zone (for many TLDs, at the registry operator). This record "glues" the nameserver's name to its IP address, so the resolver immediately receives the complete information and can continue the lookup.

Practical application

Glue records are configured mainly when a domain owner runs their own nameservers within the same domain. This applies to hosting providers and companies that prefer not to rely on external DNS services and instead maintain branded nameservers such as ns1.brand.com and ns2.brand.com.

The entries are created in the registrar's panel, in the section for registering nameservers (sometimes called "host records" or "child nameservers"). Keep in mind that changing glue records is subject to normal DNS propagation and can take up to 48 hours for the new values to spread across the internet. Misconfigured glue records make the entire domain unreachable, so their setup deserves especially careful verification.