In a BIG-IP High Availability (HA) environment, most configuration objects (Virtual Servers, Pools, iRules) are considered "shared" and are synchronized automatically between devices. However, network-level objects—specifically VLANs and Self IPs—are unique to the hardware and are generally not synchronized by the ConfigSync process.

This is intentional because two devices in a cluster may have different physical cabling or interface assignments. For example, Cluster Member A might use interface 1.1 for a specific VLAN, while Cluster Member B might use interface 1.2. Because the BIG-IP system cannot assume that the physical network topology is identical for both appliances, the administrator must Configure the new VLAN manually on Cluster Member B.

Once the VLAN is created manually on both devices with the exact same name, it can then be used to host "shared" floating Self IP addresses or traffic groups that will synchronize. Failing to create the VLAN on the peer device will prevent the traffic group from failing over correctly, as the peer will not have the necessary Layer 2 broadcast domain defined to take over the traffic. Resetting Device Trust (Option D) is a drastic step for fix sync communication issues but will not change the fact that VLANs are non-syncable objects. Enabling the interface (Option B) only affects the link status of Member A and has no impact on the configuration of Member B.