Serving a zone reliably.
WHAT RELIABILITY REQUIRES
Several servers On separate networks In separate locations With diverse routing
WHY SEPARATE NETWORKS
Two nameservers on one network fail together.
WHAT PRIMARY AND SECONDARY MEAN
The primary holds the editable zone; secondaries transfer it.
WHAT A HIDDEN PRIMARY IS
A primary not published in the zone's nameserver records, so it is not queried directly.
WHY THAT HELPS
It reduces exposure while remaining the source of truth.
WHAT ZONE TRANSFER DOES
Copies the zone to secondaries.
WHAT TO SECURE IT WITH
Shared-key authentication, and restriction by address.
WHY
An open transfer discloses your entire zone.
WHAT NOTIFICATION DOES
Tells secondaries a change has occurred, rather than waiting for the refresh interval.
WHAT THE SERIAL NUMBER CONTROLS
Whether secondaries consider their copy stale.
WHAT HAPPENS IF IT IS NOT INCREMENTED
Changes never propagate to secondaries.
WHAT TO MONITOR
That every nameserver returns the same serial That every one responds That expiry is not approaching
