Redundant topologies based on switches and bridges are susceptible to broadcast storms, multiple frame transmissions, and MAC address database instability. Therefore network redundancy requires careful planning and monitoring to function properly.

Switched networks provide the benefits of smaller collision domains, microsegmentation, and full duplex operation. Switched networks provide better performance.

Redundancy in a network is required to protect against loss of connectivity due to the failure of an individual component. Providing this redundancy, however, often results in physical topologies with loops. Physical layer loops can cause serious problems in switched networks. Broadcast storms, multiple frame transmissions, and media access control database instability can make such networks unusable.

The Spanning-Tree Protocol is used in switched networks to create a loop free logical topology from a physical topology that has loops. Links, ports, and switches that are not part of the active loop free topology do not participate in the forwarding of data frames. The Spanning-Tree Protocol is a powerful tool that gives network administrators the security of a redundant topology without the risk of problems caused by switching loops.

Students completing this module should be able to:

• Define redundancy and its importance in networking
• Describe the key elements of a redundant networking topology
• Define broadcast storms and describe their impact on switched networks
• Define multiple frame transmissions and describe their impact on switched networks
• Identify causes and results of MAC address database instability
• Identify the benefits and risks of a redundant topology
• Describe the role of spanning tree in a redundant-path switched network
• Identify the key elements of spanning tree operation
• Describe the process for root bridge election
• List the spanning-tree states in order
• Compare Spanning-Tree Protocol and Rapid Spanning-Tree Protocol