Who is authoritative.
WHAT NAMESERVERS ARE
The servers holding a domain's records.
WHERE THEY ARE SET
At the registrar, in the domain's settings.
WHAT DELEGATION MEANS
The registry directing queries for your domain to your nameservers.
WHAT CHANGING THEM DOES
Moves authority to a different set of servers.
Every record must exist at the new ones before you change.
WHY THAT ORDER MATTERS
Changing first and adding records afterwards causes an outage.
WHAT GLUE RECORDS ARE
Address records for nameservers within the domain they serve.
Needed to break the circular dependency.
Usually handled for you.
WHAT TO CHECK AFTER CHANGING
That the domain resolves That mail flows That every service still works
HOW LONG IT TAKES
Longer than an ordinary record change, because nameserver information is cached at the registry level.
WHAT TO AVOID
Changing nameservers without recording the existing records Changing them during a busy period
WHAT TO KEEP
The old records, until you are certain.
