Delegating part of a domain.
WHAT DELEGATION IS
NS records for a subdomain pointing at different nameservers, so queries for that subdomain are answered elsewhere.
WHEN YOU NEED IT
A subdomain managed by a different provider A service requiring control of a subdomain A separate environment with its own DNS
HOW TO SET IT UP
Add NS records for the subdomain in your main zone, listing the other provider's nameservers.
Remove any A or CNAME record for that subdomain, which would conflict.
WHAT THIS MEANS
You no longer control that subdomain's records in your own zone. Changes must be made where it is delegated.
WHEN NOT TO USE IT
For an ordinary subdomain on your own hosting. An A record is correct and simpler.
Delegation adds complexity and a dependency on another provider.
CHECKING IT
A lookup for the subdomain's NS records confirms the delegation.
A lookup for the subdomain itself should return whatever that provider publishes.
THE COMMON CONFUSION
A delegated subdomain not resolving because the other provider has no zone for it.
Both sides must be configured.
