CCNP Routing and Switching TSHOOT 300-135: Official Cert Guide

Reviewing STP Operation

STP uses Bridge Protocol Data Units (BPDUs) to build the STP topology. BPDU packets contain information on ports, addresses, priorities, and costs needed to build the STP topology and ensure that the data ends up where it was intended to go. BPDU messages are exchanged every 2 seconds by default across switches to detect loops in a network topology. The loops are then removed by logically blocking selected bridge interfaces and placing them in the blocked state.

STP prevents Layer 2 loops from occurring in a network, because such an occurrence could result in a broadcast storm or the corruption of a switch’s MAC address table. Switches in an STP topology are classified as one of the following:

Root bridge: The root ...