What must a switch do when it transitions from classic STP to RSTP?

When a switch transitions from classic Spanning Tree Protocol (STP) to Rapid Spanning Tree Protocol (RSTP), it specifically needs to update all port configurations to accommodate the different mechanisms and functionalities that RSTP introduces. RSTP is designed to provide faster convergence times compared to classic STP by using enhanced port roles and states, which requires an adjustment of the switch's port parameters.

Updating port configurations ensures that all ports are appropriately set to take advantage of RSTP’s capabilities, such as the ability to transmit BPDU frames more effectively and adjust their roles based on the network topology. RSTP employs a more efficient protocol for determining the network topology, so maintaining consistent and updated configurations across all ports is critical for it to function correctly.

The other options do not accurately align with the requirements of transitioning to RSTP. For instance, rebooting the switch is not necessary solely for the protocol change, nor is it required that all devices on the network support RSTP for a switch to operate in RSTP mode. Finally, switching to static addressing is unrelated to the protocol mechanics and does not factor into the transition from STP to RSTP.