3Com 3 manual Traffic flowing through Bridge B

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36CHAPTER 4: USING RESILIENCE FEATURES

Figure 7 Traffic flowing through Bridge B

STP determines which is the most efficient path between each bridged segment and a specifically assigned reference point on the network. Once the most efficient path has been determined, all other paths are blocked. Therefore, in Figure 5, Figure 6, and Figure 7, STP initially determined that the path through Bridge C was the most efficient, and so blocked the path through Bridge B. After the failure of Bridge C, STP re-evaluated the situation and opened the path through Bridge B.

How STP Works When enabled, STP determines the most appropriate path for traffic through a network. It does this as outlined in the sections below.

STP Requirements Before it can configure the network, the STP system requires:

■Communication between all the bridges. This communication is carried out using Bridge Protocol Data Units (BPDUs), which are transmitted in packets with a known multicast address.

■Each bridge to have a Bridge Identifier. This specifies which bridge acts as the central reference point, or Root Bridge, for the STP system — the lower the Bridge Identifier, the more likely the bridge is to become the Root Bridge. The Bridge Identifier is calculated using the MAC address of the bridge and a priority defined for the bridge. The default priority of your Switch is 32768.

■Each port to have a cost. This specifies the efficiency of each link, usually determined by the bandwidth of the link — the higher the

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Contents SuperStack 3Com Corporation 5400 Bayfront Plaza Santa Clara, California Contents Using Multicast Filtering Status Monitoring and Statistics IP Addressing About this Guide Conventions List conventions that are used throughout this guideRelated DocumentationComments Pddtechpubscomments@3com.comProduct RegistrationSwitch Features Page What is Switch FeaturesManagement Software?Switch Features Overview Ports operating at 1000 Mbps only support full duplex mode For more information about multicast filtering, see UsingDuplex Flow ControlFor more information about STP and RSTP, see Using Resilience FeaturesQuality of Service For more information about Quality of Service, see UsingEvent Notification For more information about VLANs, see Setting Up Virtual Port Features Ports operating at 1000 Mbps support full duplex mode only Port Features Switch units connected using an aggregated link Aggregated Links Traffic Distribution and Link Failure on Aggregated Links 2 Gbps aggregated link between two Switch units Optimizing Bandwidth Using Multicast Filtering Relevant multicast groupUsing Multicast Filtering Query mode Snooping ModeQuery Mode Igmp v2 protocol That support IPIgmp multicast filtering works as follows Enabling Igmp Multicast LearningIgmp Multicast Filtering Using Multicast Filtering Spanning Tree Protocol STPNetwork Ieee 802.1w standard What is STP? Traffic flowing through Bridge B Port Speed Link Type Path Cost 802.1D-1998 802.1w Using Resilience Features Port costs in a network Configuration 1 Redundancy for Backbone Link Configuration 2 Redundancy through Meshed BackboneConfiguration 3 Redundancy for Cabling Error STP configurations Default Behavior Using STP on aNetwork with Multiple VLANsConfiguration that separates VLANs Using Resilience Features What is the Switch How SwitchDatabase? Database EntriesSwitch Database Entry States Databases entries can have three statesWhat is Traffic Prioritization?Available Converged network applications Used by organizations with a802.1D Priority Levels How Traffic Prioritization Works Your Switch Traffic PrioritizationHow traffic is processed to provide Quality of Service Configuring traffic prioritization for QoS on a SwitchUsing Traffic Prioritization What is RMON? Network efficiency and reduce the load on your networkThat allows you to monitor the traffic of LANs or VLANs Alarms EventsIt improves your efficiency Switch RmonLow Threshold Statistic High Threshold Recovery Period Low Threshold Statistic High Threshold Recovery Status Monitoring and Statistics Hardware Status Monitoring Example device summary web Setting UP Virtual Lans VLANs ease the movement of devices on networks VLANs provide extra securityVLANs help to control traffic Membership Creating an Ieee 802.1Q Tagged LinkTwo Vlans connected via a router Configuration Using UntaggedConfigure the VLANs ExamplesConfigure the VLANs on Switch Add endstation ports on Switch 1 to the VLANsAdd ports to the VLANs Add port 12 on Switch 1 to the VLANs Add endstation ports on Switch 2 to the VLANsAdd port 11 on Switch 2 to the VLANs Check the Vlan membership for both switchesConfiguration How Your Switch Obtains IPInformation How Automatic IPHow Automatic IP Configuration Works Automatic IP configuration feature That a Switch may change its IP address whilst in useConsiderations Configuration Rules IP AddressingGlossary IndexPage Configuration Rules Configuration Rules for Gigabit EthernetFast Ethernet configuration rules Configuration Rules for Fast Ethernet Appendix a Configuration Rules Network This chapter contains the following sectionsSegments are connected to the Switch which is positioned Simple NetworkFamily and 4900 family can be used in your network ExampleDual Speed Hub Switch Advanced Network ImprovingResilience of Your NetworkEnhancing PerformanceTherefore the overall network performance IP Addresses Simple OverviewObtaining a Registered IP Address IP AddressDotted Decimal Notation Decimal value of an octet whose bits are all 1s isNetwork Portion Subnet mask Subnet Mask Numbering Extending the Network PrefixOr leave the field blank Glossary Glossary Endstation EthernetEthernet address Fast EthernetGateway Half duplexHub Ieee 802.1DLine speed See baud Glossary Rstp See Rapid Spanning Tree Protocol STP See Spanning Tree Protocol STP Page Glossary Index NumbersIgmp multicast filtering 30 Internet Addresses 85 InterNIC Sub-networks. See subnets Switch Database

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