Cisco Certified Network Professional 2026 – 400 Free Practice Questions to Pass the Exam

The max age timer in Spanning Tree Protocol (STP) is crucial for managing the lifespan of Bridge Protocol Data Units (BPDUs). Specifically, this timer dictates how long a switch should retain the information it receives in a BPDU before it is deemed outdated. When BPDUs are transmitted, switches interpret the information to determine the network topology and make decisions about port roles.

Once the max age timer expires, a switch considers the received BPDUs stale or invalid, leading it to initiate the process of sending new BPDUs to gather fresh topology information. This is fundamental for maintaining a reliable and loop-free network structure, ensuring that changes in the network topology are accurately reflected in the STP decisions.

The other options relate to different functionalities within the STP process. For example, controlling the time a port remains in a forwarding state is more related to the forward delay timer, and setting durations for learning phases is managed through different timers as well.