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RSPAN, or Remote Switched Port Analyzer, is a Cisco technology used to extend port mirroring capabilities across multiple switches in a network. It allows for the monitoring of traffic from a source port on a switch and sends that mirrored traffic to a destination port on another switch. However, there are certain types of traffic that are not eligible for mirroring due to the potential for causing network issues or because they do not operate in a way that allows for effective mirroring.

In this case, Bridge Protocol Data Units (BPDUs) used in Spanning Tree Protocol (STP) are a type of control traffic that is critical for the functioning of the Spanning Tree algorithm. These messages help to prevent loops in the network topology and ensure that the network remains stable. When RSPAN is configured, BPDUs are not mirrored to maintain the integrity and operation of the Spanning Tree. If they were mirrored, it could lead to the risk of creating loops or misconfigurations across the broader network, which could have detrimental effects.

Other types of traffic like ICMP (Internet Control Message Protocol), TCP (Transmission Control Protocol), and UDP (User Datagram Protocol) packets are not subjected to such restrictions and can be mirrored by RSPAN, allowing network