When a fabric has multiple Subnet Managers, you must configure some parameters uniquely and some identically.
Subnet Manager Priority – Subnet Managers can have different Priority values. The overall priority is determined from both the gateway's GUID and the Priority value. Configure the Subnet Manager with the highest Priority value first, and then configure any remaining Subnet Managers.
Subnet Manager Prefix – All Subnet Managers must use the same prefix. Configure the standby Subnet Managers first, and then configure the master Subnet Manager.
Subnet Manager Controlled Handover – All Subnet Managers must use the same configuration for controlled handover. Configure the standby Subnet Managers first, and then configure the master Subnet Manager.
Subnet Manager Routing Algorithm – All Subnet Managers must use the same routing algorithm. Configure the standby Subnet Managers first, and then configure the master Subnet Manager.