Glue records: solving DNS’s chicken-and-egg problem

Suppose example.com is served by ns1.example.com. To resolve anything under example.com you must first find ns1.example.com’s address — which lives under example.com. Loop. Glue records are the fix: the PARENT zone (.com) publishes the IP address of ns1.example.com alongside the delegation, so resolvers can bootstrap.

dig @a.gtld-servers.net example.com NS +norecurse
# a seção ADDITIONAL traz o glue (os IPs dos NS), quando ele existe

When you need it — and when you do not

• Nameserver INSIDE the delegated domain (ns1.example.com for example.com): glue is mandatory. It is entered at the registrar, usually as "host records" or "child nameservers".
• Nameserver in another domain (ns1.dns-provider.com for example.com): no glue needed — the resolver finds the address through the provider’s own domain.

The classic trap: you renumber your nameserver and update the A record in your zone — but forget the glue at the registrar. Resolvers keep receiving the OLD address from the parent, and the domain fails intermittently in ways that look impossible. If your nameservers use in-domain names, every IP change happens in two places: the zone and the glue.