Glue records

Name servers in delegations appear listed by name, rather than by IP address. This means that a resolving name server must issue another DNS request to find out the IP address of the server to which it has been referred.

Since this can introduce a circular dependency if the name server referred to is under the domain that it is authoritative of, it is occasionally necessary for the name server providing the delegation to also provide the IP address of the next name server. This record is called a glue record.

In practice, glue records are used for 2 purposes:

1. To speed up queries - and consequently reduce DNS load - by providing the name and IP addresses (the glue) for all authoritative name servers, both within and external to the domain.
2. To break the query deadlock for referrals which return name servers within the domain being queried.

In order to create a Glue Record, a NS and an A record are needed. They should meet the following requirements:

• The NS record must NOT have a corresponding A record;
• The A record MUST be defined on $ORIGIN or on a subdomain of $ORIGIN.

The table below contains an example of the records required for creating a Glue Record.

Table 4.1. Required Records

In order to create a Glue Record, you need to select the desired zone name from the zones list and click the Glue Records link at the top of the table.

Table 4.2. Resulting Glue Record