Original subtitles

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In this video, we're going to discuss Spanning Tree

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Spanning Tree was developed to stop a layer 2 loops occurring in switch environments.

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In transparent switching or transparent bridging which is what Ethernet uses

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redundant links introduce loops and Spanning Tree is used to stop those loops.

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Spanning Tree has been around for many years

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and there been multiple developments and enhancements.

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So this is one of the challenges that you’re going to face.

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There are different implementations and version of Spanning Tree

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and you'll need to know some of those differences.

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Spanning Tree are very important protocol in traditional networks

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and once again its primary purpose is to stop loops in the switch environment

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and not necessarily to stop them as quickly as we would like.

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Spanning Tree was developed many years ago

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originally being developed for bridges rather than switches

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and thus at times a very slow to converge.

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In other words, it takes a long time for traffic to be re-routed

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if there’s a change in the network topology.

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Spanning Tree was once again originally developed for bridges

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and bridges do their calculations in software rather than in hardware

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which is what switches do today.

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So in the past, slower convergence was fine

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but that’s a major problem in today’s environments, where we run Voice over IP

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or other protocols that require very quick convergence.

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Thus the original standard Spanning Tree or 802.1D Spanning Tree

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has been superseded by newer versions

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such as Rapid Spanning Tree and Multiple Spanning Tree.

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because Spanning Tree is of great importance for the CCNA certification

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as well as for real deployments

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I’m going to start off with original version of Spanning Tree

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802.1D and then we'll build on those concepts looking at more and more

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complex topologies and other versions of Spanning Tree.