Registered hosts and glue records
When a name server tries to resolve the IP address of a host, like example.com it must look up the IP address from the name server for the host. If the name server for the host is a subdomain of the host itself, such as ns1.example.com, the lookup can result in a circular dependency, where the first name server has to know the IP address of example.com to get resolve the IP address of the name server, ns1.example.com in order to look up the address of example.com.
Registered hosts or "Glue records" are a way of making the IP address of the name server known when it is a subdomain of the domain for which it serves. For example, If your domain is example.com and your name servers are ns1.example.com, ns2.example.com, ns3.example.com, and ns4.example.com, you would create four registered host records linking each name server to its IP address.
When to use registered hosts (glue records)
Use registered hosts when your name servers are subdomains of your domain.
Setting up registered hosts
- On the DNS tab , scroll down to Registered hosts.
- Enter the name of the name server or host you want to register and the IP address.
If you want to use IPv6, click Add an IPv6 address and enter the address.
- Click Add to create the record.
You can edit and delete registered host records with the Edit and Delete buttons. Make sure the host is not currently in use by this domain. Check the Name servers section immediately above the Registered hosts.
Transferring in glue records
When you transfer in a domain that has glue records configured, Google Domains will try to create registered host records. Check the registered host entries after you complete the transfer in process.
Unable to delete registered hosts
If you are unable to delete or save changes to a registered host record, it may still be linked to the domain. Check the Name servers section above the Registered hosts section on the DNS tab and delete or change the name server record that contains the host you are editing or deleting.