Glossary

Glue Record

Breaks the circular dependency when a nameserver is within the domain it serves

A glue record is an A or AAAA record provided by a parent zone's nameserver that supplies the IP address of a child zone's nameserver when that nameserver's hostname falls within the domain being delegated, resolving what would otherwise be a circular DNS dependency.

What is a Glue Record?

A glue record is a special DNS record that exists to solve a circular dependency problem in DNS delegation. When a domain's authoritative nameservers have hostnames within the same domain — for example, "ns1.example.com" is a nameserver for "example.com" — a resolver would need to know the IP address of "ns1.example.com" to find the nameservers for "example.com," but it would need to query "example.com's" nameservers to look up the IP of "ns1.example.com." This is a circular reference.

Glue records break this circularity. They are A (or AAAA) records for the nameserver hostnames that are provided directly in the delegation response from the parent zone (for example, the ".com" TLD nameservers), in the "Additional" section of the DNS response. This way, the resolver receives both the NS records and the IP addresses of those nameservers in a single response, without needing to make any additional queries.

Glue records are configured at the domain registrar when you register or update nameservers whose hostnames are within your own domain.

When Are Glue Records Required?

Glue records are required whenever a nameserver's hostname is within the zone being delegated. If you are using your own domain as the nameserver — for example, running your own DNS infrastructure at "ns1.yourdomain.com" — you must register glue records with your registrar so the parent zone can serve the nameserver's IP address alongside the delegation.

If you are using a third-party DNS provider whose nameservers are in a different domain — for example, "ns1.dnsprovider.com" — no glue records are needed in your zone, because the IP address of those nameservers can be looked up through a separate, non-circular query path for "dnsprovider.com."

Missing or incorrect glue records cause resolution failures for the entire domain. If the glue record IP is wrong or absent, resolvers cannot contact the authoritative nameservers and the domain becomes unreachable.

How to Check Glue Records

You can verify the glue records associated with your domain's nameservers using the NS Lookup tool at nslookup.net/tools/ns-lookup. The tool queries the parent TLD nameservers for your domain's delegation and shows the NS records together with any glue A records returned in the Additional section of the response.

If you are setting up self-hosted nameservers, confirm with your registrar that glue records have been registered for each nameserver hostname before updating your domain's NS records.

Related Tool

NS Lookup

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Frequently Asked Questions

Do I need glue records if I use Cloudflare or another DNS provider?

No. If you use a third-party DNS provider like Cloudflare, Route 53, or Google Cloud DNS, their nameservers (e.g., "ns1.cloudflare.com") are in a different domain from yours. Resolvers can look up the IP addresses of these nameservers independently without circular dependency. You only need glue records when your nameservers are hosted within the domain they serve.

Where do glue records live in DNS?

Glue records are stored and served by the parent zone's nameservers, not by the child zone itself. For a .com domain, the glue records are stored in the .com TLD nameservers operated by Verisign. They are registered through your domain registrar, which submits them to the registry. You will not see them in your own zone file.

What happens if a glue record is outdated?

If a glue record contains an old IP address for your nameserver, resolvers that contact that IP will either get no response (if the old IP is no longer in use) or an incorrect response (if it is now used by a different server). This results in DNS resolution failures for your entire domain. Always update glue records at your registrar before or simultaneously with changing your nameserver IP addresses.

Can a domain have multiple glue records?

Yes. Each nameserver hostname requires its own glue record. If your domain uses "ns1.yourdomain.com" and "ns2.yourdomain.com," you need to register glue A records for both hostnames. If your nameservers support IPv6, you should register both A (IPv4) and AAAA (IPv6) glue records for each nameserver.