A Subnet Can Have More Than One SM

A subnet may contain more than one SM, but only one SM is permitted to manage the devices in the subnet. This SM is referred to as the Master SM. Any other SMs are in one of two possible states:

• Standby SM. Standby SMs do not manage the subnet. Rather, they periodically poll the Master SM—via a SubnGet(SMInfo)—to obtain the ActCount element to determine if it is still actively managing the subnet or has failed.

• Inactive SM. An Inactive SM does not poll the Master SM's ActCount. However, it will respond to a command (referred to as a Control Packet) that causes it to change from the Inactive state to another state (e.g., the Standby state).