DNS/RFC/6761について、ここに記述してください。
Special-Use Domain Names https://tools.ietf.org/html/rfc6761
This document specifies under what circumstances special treatment is
- appropriate, and in what ways.
6.2. Domain Name Reservation Considerations for "test."
6.3. Domain Name Reservation Considerations for "localhost."
6.4. Domain Name Reservation Considerations for "invalid."
6.5. Domain Name Reservation Considerations for Example Domains
1. Users SHOULD understand that example names are reserved for use in documentation.
2. Application software SHOULD NOT recognize example names as
special and SHOULD use example names as they would other domain names.
7. DNS Registries/Registrars MUST NOT grant requests to register
example names in the normal way to any person or entity. All
example names are registered in perpetuity to IANA: