Refer to Figure 30-2 on page 860. There are three circumstances under which an SM enters the Discovering state:
If it doesn't get a response from the Master SM when it performs a SubnGet(SMInfo) to read the Master's SMInfo.ActCount element.
Upon receipt of a SMP Control Packet commanding it to enter the Discovering state.
Once it has entered the Discovering state, the SM uses SMPs to discover all of the nodes in the subnet. During this process, the SM may or may not encounter another device that contains an SM. There are two possible cases:
Case 1. No other SMs. If it has completed ...