Normal Operation:The active node has a higher priority (e.g., 100) than the passive node (e.g., 90), set during HA configuration.
Force Failover:In Grid Manager (Grid > Members > Force Failover), the admin triggers a manual switch. The active node sends a VRRP advertisement withpriority 255to assert itself as the master, then lowers its priority (e.g., to 90), allowing the passive node (now higher, e.g., 100) to take over.
Why 255:Per VRRP standards (RFC 3768), 255 is the highest priority, reserved for the master to signal ownership or force transitions. Post-failover, priorities revert to configured values.
Options:
A (0):Signals a node is shutting down, not forcing failover. Incorrect.
C (1024):Exceeds VRRP’s 8-bit range (0-255). Invalid.
D (128):A possible priority, but not the forced failover value. Incorrect.
Practical Example:In an INE lab, you’d force failover, capture VRRP packets (e.g., with Wireshark), and verify the 255 priority, troubleshooting HA behavior.References:Infoblox NIOS Administrator Guide – HA Failover; RFC 3768 (VRRP); INE Course Content: NIOS DDI Grid Troubleshooting.
