In a BIG-IP high availability (HA) configuration, Auto-Sync is a device trust feature that automatically synchronizes configuration changes from the Active device to the Standby device within a Sync-Failover device group.
Key principles from BIG-IP Administration Data Plane Concepts:
The Active device is always the authoritative source of configuration
Configuration changes are intended to be made only on the Active device
With Auto-Sync enabled, any time the Active device configuration changes, the system automatically pushes the configuration to all Standby members of the device group
Configuration changes made directly on a Standby device are not preserved
In this scenario:
The administrator modifies a Virtual Server on the Standby device
That change is local only and does not alter the device group’s synchronized configuration
When Auto-Sync next runs (triggered by a change on the Active device or an internal sync event), the Active device configuration overwrites the Standby configuration
As a result, the configuration change made on the Standby device is undone.
Why the Other Options Are Incorrect:
A – The change is not undone only when another change is made; it is undone during the next Auto-Sync operation
B – Changes made on the Standby device are never propagated to the Active device
D – Auto-Sync does not merge or promote Standby changes into the HA pair configuration
Best Practice Reinforced:
Always perform configuration changes on the Active BIG-IP device when Auto-Sync is enabled to ensure consistent and predictable HA behavior.
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