What is the duration for an interface in a learning state following a root electionchange?

When a switch interface enters the learning state following a root election change, it is a crucial part of the Spanning Tree Protocol (STP) operation. In this phase, the interface is allowed to learn MAC addresses from received frames but is not yet forwarding frames. The interface remains in the learning state for 15 seconds. This time allows the switch to gather sufficient information about the network topology and MAC addresses before it transitions to the forwarding state.

The 15-second duration is important because it helps prevent loops in the network and allows for stable learning of the network structure. After this period, if the conditions that led to the root election change have stabilized, the port can move to a forwarding state where it starts to process and forward traffic.

While other options suggest different timeframes, they do not align with the standard behavior defined by the Spanning Tree Protocol regarding the learning state duration. The 15 seconds is a well-established interval that plays a critical role in ensuring network stability and efficiency during topology changes.