Which RSTP port role is a discarding port that receives a superior BPDU from the same switch?

The correct answer is that the port role in question is called a Backup port. In Rapid Spanning Tree Protocol (RSTP), a Backup port is used when a switch has multiple paths towards the same segment, and one path is designated as the active path while the other operates in a discarding state to prevent loops.

When a switch receives a superior Bridge Protocol Data Unit (BPDU) on a port that is in the Backup role, it acknowledges that the incoming BPDU indicates a more favorable configuration of the network. Although the Backup port is not actively forwarding traffic, it is in a standby state, ready to take over should the designated port fail. This unique characteristic ensures redundancy and faster convergence times, which are critical for maintaining network reliability.

In contrast, other port roles like Alternate and Designated serve different functions. The Alternate port provides a backup link to the Root Bridge but does not directly connect to a particular network segment like a Backup port does. The Designated port is responsible for forwarding traffic towards a particular segment and maintains the lowest cost to the Root Bridge. The Root port is the port on a switch that has the best path to the Root Bridge. Each of these roles has distinct behaviors, emphasizing how RSTP manages redundancy and loop