This tutorial will explain what stealth nameserver records are

Stealth nameserver records are sent when the authoritative zone file has been delegated to a different pair of nameservers.

e.g, at the registrar, I delegate the following nameservers for myfastdotdomain.com:

ns1.fastdot.com.au
ns2.fastdot.com.au

However, when a user queries the nameservers, they inform the user that the zone has been delegated elsewhere under the following nameservers:

ns1.myfastdotdomain.com
ns2.myfastdotdomain.com

The user then queries the delegated nameservers for the appropriate records and the lookup is completed.

Additional Information

1. Although Stealth NS records are valid, they can sometimes indicate a problem in your zone configuration.

For example, Stealth NS records can be sent if only 2/3 of your ‘hypothetical’ nameservers are configured at the registry, and all 3/3 nameservers are assigned as authoritative within your zone file; this will cause 1/3 of your nameservers to be sent as a Stealth NS record.

2. Stealth NS records can be created by using the NS Resource Record in your zone-file. Here is an example of how your zone file might look if you had stealth NS records:

At the registrar:

myfastdotdomain.com IN NS ns1.fastdot.com.au
myfastdotdomain.com IN NS ns2.fastdot.com.au

In the zone file:

myfastdotdomain.com IN NS ns1.myfastdotdomain.com
myfastdotdomain.com IN NS ns2.myfastdotdomain.com