Cabletron Systems SmartSTACK ELS100-S24TX2M Management Manual

Also see for SmartSTACK ELS100-S24TX2M: Quick installation guide Quick installation guide User guide

Contents

88 Spanning Tree Concepts ELS100-S24TX2MSpanning Tree Protocol OperationWhen the Spanning Tree Protocol is enabled for the first time or whenthere is a change in the network topology, such as a failure or the additionor removal of a component, the Spanning Tree Protocol automaticallysets up the active topology of the current network.Communicating Between BridgesPeriodically, all devices running the Spanning Tree Protocol on a networktransmit packets to each other “in care of” the Bridge Group Addresswhich all bridges share. When a bridge receives a frame sent to theBridge Group Address, the bridge’s Spanning Tree Protocol processesthe packet. Application software and other LAN segments ignore thepacket. Bridges communicate between each other in order to determinethe Root Bridge.Selecting a Root Bridge and Designated BridgesDuring communication between bridges, one bridge is determined tohave the lowest bridge identifier. This bridge becomes the Root Bridge.After the Root Bridge has been selected, each LAN segment looks for thebridge that has the lowest cost relative to the Root Bridge. These bridgesbecome Designated Bridges.Selecting Designated PortsEach Designated Bridge selects a Designated Port. This port isresponsible for forwarding packets to the Root Bridge.Handling Duplicate PathsWhen the active topology of the network is determined, all packetsbetween any two nodes in the network use only one path. Where aduplicate path exists, the non-designated port is put into a blocking state.Remapping Network TopologyIf there is a change in the network topology due to a failure or the removalor addition of any active components, the active topology also changes.This may trigger a change in the state of some blocked ports.