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Copyright 2003 Redundancy Redundant networking topologies are designed to ensure that networks continue to function in the presence of single points of failure.
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CCNA 3 Chapter 8 Spanning Tree Protocol
ByYour Name
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Objectives
• Redundant topologies• Spanning Tree Protocol
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RedundancyRedundant networking topologies are designed to ensure that networks continue to function in the presence of single points of failure.
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Redundant Topologies
• A goal of redundant topologies is to eliminate network outages caused by a single point of failure.
• All networks need redundancy for enhanced reliability.
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Redundant Switched Topologies
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Broadcast Storms
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Multiple Frames Transmission
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MAC Database Instability
In a redundant switched network, it is possible for switches to learn the wrong information. A switch can learn that a MAC address is on a port when it is not.
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Spanning Tree Protocol
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Bridging Loops for Redundancy
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Spanning Tree
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Spanning-Tree Costs
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Spanning-Tree Operation
• One root bridge per network.
• One root port per nonroot bridge.
• One designated port per segment.
• Nondesignated ports are unused.
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Selecting the Root BridgeBridge protocol data unit (BPDU)
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Spanning-Tree Port States
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Spanning-Tree Recalculation
A switched internetwork has converged when all the switch and bridge ports are in either the forwarding or blocked state.
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Rapid Spanning Tree Protocol
• Clarification of port states and roles
• Definition of a set of link types that can go to forwarding state rapidly
• Allowing switches, in a converged network, to generate their own BPDUs rather than relaying root bridge BPDUs
The Rapid Spanning Tree Protocol, IEEE 802.1w, will eventually replace the Spanning Tree Protocol, IEEE 802.1D.
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