Spanning tree protocol

Based on an algorithm invented by Radia Perlman while working for Digital Equipment Corporation, Spanning Tree Protocol Is an OSI layer-2 protocol which ensures a loop free topology for any bridged LAN. The Spanning Tree Protocol (STP), is defined in the IEEE Standard 802.1D. As the name suggests, it creates a spanning tree within a mesh network of connected layer-2 bridges (typically ethernet switches), and disables the links which are not part of that tree, leaving a single active path between any two network nodes.
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