Hack the Route Start free Open app Names and DNS
Zone transfer
How a secondary name server copies a zone from its primary: whole (AXFR) or just the changes (IXFR), prompted by NOTIFY.
The primary holds the zone file; secondaries hold copies, so the names survive a server failing. A
secondary asks for the whole zone (AXFR, over TCP), then compares the SOA serial at each refresh or on a
NOTIFY from the primary, and fetches only what changed (IXFR). An edit without a higher serial never leaves the
primary. A transfer lists every name in the zone, so every server holding it must restrict who may ask
(allow-transfer, ideally with a TSIG key).