glue record
also: glue A record, glue AAAA record
A DNS record that provides the IP address of a nameserver listed in a parent zone's NS records, breaking a circular dependency when a nameserver is within the delegated subdomain.
A glue record is an A or AAAA record in a parent DNS zone that maps a nameserver hostname to its IP address. It solves the problem of circular dependencies that arise when a domain's authoritative nameserver has a hostname within that same domain.
For example, if example.com delegates to nameserver ns1.example.com, a recursive resolver cannot look up ns1.example.com's IP address without already knowing the nameserver for example.com. The parent zone (.com) includes a glue record pointing ns1.example.com to its IP address, allowing resolution to bootstrap.
Glue records are typically seen when querying root or TLD nameservers with dig +trace, appearing in the additional section of DNS responses alongside NS records.