Active Device Election at the first set up HA Failover

Hi All,

When I test HA configuration on my lab (VE), TMOS 11.6. The which I create Group HA with Sync-Failover type and force the initial sync will be the Active Device after that. But when I deploy as the same in production with VIPRION 2200 (Blade 2150), TMOS 11.6, the which I create Group HA with Sync-Failover type and force the initial sync will be the Standby Device and the was the Active Device. Although the active/standby device will be change by modified traffic group setting, but I really want to know how two devices elect the Active one. Could anyone help me? Best regard, Loan.