STP Application
On a complex network, loops are inevitable. With the requirement for network redundancy backup, network designers tend to deploy multiple physical links between two devices, one of which is the master and the others are the backup. Loops are likely or bound to occur in such a situation. Loops can cause flapping of MAC address tables and therefore damages MAC address entries.
On the network shown in Figure 1, after CE and PE running STP discover loops on the network by exchanging information with each other, they trim the ring topology into a loop-free tree topology by blocking a certain port. In this manner, replication and circular propagation of packets are prevented on the network and the switching devices are released from processing duplicated packets, thereby improving their processing performance.