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BCMSN Exam Cram™ 2 (Exam Cram 642-811) by Richard A. Deal

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Running the STP Algorithm

When STP is run, one of its first jobs is to designate a root switch. After this is chosen, each switch will calculate the shortest distance (best cost) to the root. For each LAN segment, a designated switch will be chosen based on the switch that has the best cost. Ports that provide redundant connections to the root are blocked, leaving a single path to the root, thus effectively eliminating any loops. The following sections explain this process in more detail.

Root Switch Election Process

One of the first tasks of STP is to elect the root switch. Switches sharing BPDUs will discover the current topology of the network, including all the switch identifiers. A switch's identifier consists of a 2-byte priority and a ...

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