Do interfaces in a blocking state send Bridge Protocol Data Units (BPDUs)?

In the context of the Spanning Tree Protocol (STP), interfaces that are in a blocking state do not forward frames and do not actively participate in the network. However, they are still responsible for maintaining the STP topology and ensuring that the network does not form loops.

Even though interfaces in a blocking state do not forward data frames, they still need to communicate their status and information about the network topology. Therefore, these interfaces can still send and receive Bridge Protocol Data Units (BPDUs). This allows the switch to participate in the STP process and maintain information about network topology changes, even if they are not actively passing user traffic.

This is critical for ensuring that if the network topology requires changes (such as a primary link failing), the switches can quickly reconfigure and enable interfaces that are currently blocking to transition to a forwarding state if necessary.