3Com 3 manual Using Resilience Features

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38CHAPTER 4: USING RESILIENCE FEATURES

STP Configuration After all the bridges on the network have agreed on the identity of the Root Bridge, and have established the other relevant parameters, each bridge is configured to forward traffic only between its Root Port and the Designated Bridge Ports for the respective network segments. All other ports are blocked, which means that they are prevented from receiving or forwarding traffic.

STP Reconfiguration Once the network topology is stable, all the bridges listen for Hello BPDUs transmitted from the Root Bridge at regular intervals. If a bridge does not receive a Hello BPDU after a certain interval (the Max Age time), the bridge assumes that the Root Bridge, or a link between itself and the Root Bridge, has gone down. The bridge then reconfigures the network to cater for the change. If you have configured an SNMP trap destination, when the topology of your network changes, the first bridge to detect the change sends out an SNMP trap.

CAUTION: Network loops can occur if aggregated links are manually configured incorrectly, that is, the physical connections do not match the assignment of ports to an aggregated link. RSTP and STP may not detect these loops. So that RSTP and STP can detect all network loops you must ensure that all aggregated links are configured correctly.

How RSTP Differs to RSTP works in a similar way to STP, but it includes additional information STP in the BPDUs. This information allows each bridge to confirm that it has

taken action to prevent loops from forming when it wants to enable a link to a neighbouring bridge. This allows adjacent bridges connected via point-to-point links to enable a link without having to wait to ensure all other bridges in the network have had time to react to the change.

So the main benefit of RSTP is that the configuration decision is made locally rather than network-wide which is why RSTP can carry out automatic configuration and restore a link faster than STP.

STP Example Figure 8 shows a LAN that has STP enabled. The LAN has three segments, and each segment is connected using two possible links.

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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 guideComments RelatedDocumentation Pddtechpubscomments@3com.comProduct RegistrationSwitch Features Page Management What isSwitch Features Software?Switch Features Overview Duplex Ports operating at 1000 Mbps only support full duplex modeFor more information about multicast filtering, see Using Flow ControlFor more information about STP and RSTP, see Using Resilience FeaturesEvent Notification Quality of ServiceFor more information about Quality of Service, see Using 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 Query modeSnooping Mode Igmp multicast filtering works as follows Igmp v2 protocolThat support IP Enabling Igmp Multicast LearningIgmp Multicast Filtering Using Multicast Filtering Network Spanning TreeProtocol STP 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 3 Redundancy for Cabling Error Configuration 1 Redundancy for Backbone LinkConfiguration 2 Redundancy through Meshed Backbone STP configurations Network with Default BehaviorUsing STP on a Multiple VLANsConfiguration that separates VLANs Using Resilience Features Database? What is the SwitchHow Switch Database EntriesSwitch Database Entry States Databases entries can have three statesAvailable What is TrafficPrioritization? 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 That allows you to monitor the traffic of LANs or VLANs What is RMON?Network efficiency and reduce the load on your network It improves your efficiency AlarmsEvents 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 Configure the VLANs ConfigurationUsing Untagged ExamplesAdd ports to the VLANs Configure the VLANs on SwitchAdd endstation ports on Switch 1 to the VLANs Add port 11 on Switch 2 to the VLANs Add port 12 on Switch 1 to the VLANsAdd endstation ports on Switch 2 to the VLANs Check the Vlan membership for both switchesConfiguration Information How Your SwitchObtains IP How Automatic IPHow Automatic IP Configuration Works Considerations Automatic IP configuration featureThat a Switch may change its IP address whilst in use Glossary Configuration RulesIP Addressing 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 sectionsFamily and 4900 family can be used in your network Segments are connected to the Switch which is positionedSimple Network ExampleDual Speed Hub Switch Resilience of Your Advanced NetworkImproving NetworkTherefore the overall network performance EnhancingPerformance IP Addresses Simple OverviewObtaining a Registered IP Address IP AddressNetwork Portion Dotted Decimal NotationDecimal value of an octet whose bits are all 1s is Subnet mask Subnet Mask Numbering Extending the Network PrefixOr leave the field blank Glossary Glossary Ethernet address EndstationEthernet Fast EthernetHub GatewayHalf duplex 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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