This is a Canonical Question about DNS glue records.
What exactly (but briefly) is a DNS glue record? Why are they needed and how do they work?
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A glue record is a term for a record that's served by a DNS server that's not authoritative for the zone, to avoid a condition of impossible dependencies for a DNS zone.
Say I own a DNS zone for
There's the trick. The TLD's servers will delegate to the DNS servers in the whois record - but they're within
What glue records do is to allow the TLD's servers to send extra information in their response to the query for the
I requested that this answer be merged in from a duplicate question, as the existing answers did not explain the role of the
To see how it works, type this:
This will trace the nameserver authority starting from the root servers (
Note that the authoritative nameservers for
When you ask a nameserver to supply the list of nameservers for a domain, they will often supply a list of
There is a precise (and concise) explanation on wikipedia.
Glue records are most commonly needed for users that are trying to use name server addresses that are subdomains of the domain itself. To explain a little further: John has a domain registered named domain.com. John wants to set up his own name servers (DNS) using the addresses ns1.domain.com and ns2.domain.com.
A glue record is the IP address of a name server held at the Domain Name registry.
Glue records are required when you wish to set the name servers of a domain name to a hostname under the domain name itself.
For example if you wished to set the name servers of example.com to ns1.example.com and ns2.example.com you would need to also provide the glue records (i.e. the IP addresses) for ns1.example.com and ns2.example.com.
If you did not provide the glue records for these name servers then your domain name would not work as anyone requiring DNS information for it would get stuck in a loop:
What is the name server for example.com? -> ns1.example.com What is the IP address of ns1.example.com? -> don't know, try looking at name server for example.com What is the name server for example.com? -> ns1.example.com
...and so on.
With the glue record in place the registry will hold the IP address and the loop will not occur:
What is the name server for example.com? -> ns1.example.com What is the IP address of ns1.example.com? -> [IP Address]