09-生成树协议.ppt

Broadcast Switchescontinuetopropagatebroadcasttrafficoverandover Segment1 Segment2 Server HostX RouterY Broadcast SwitchA SwitchB BroadcastStorms Complextopologycancausemultipleloopstooccur Layer2hasnomechanismtostoptheloop Server Host Workstations Loop Loop Loop MultipleLoopProblems Solution Spanning TreeProtocol Providesaloop freeredundantnetworktopologybyplacingcertainportsintheblockingstate Partof802 1dstandard Block x SwitchYDefaultPriority32768 8000hex MAC0c0022222222 SwitchXDefaultPriority32768 8000hex MAC0c0011111111 Spanning TreeProtocolRootBridgeSelection BPDU BPDU BridgeProtocolDataUnit default sentevery2seconds Rootbridge BridgewiththelowestbridgeID BridgeID Bridgepriority bridgeMACaddress Intheexample whichswitchhasthelowestbridgeID BridgeProtocolDataUnit Bridgeprotocoldataunit BPDU Spanning TreeProtocolPortCost LinkSpeedCost ReratifyIEEESpec Cost PreviousIEEESpec 10Gbps211Gbps41100Mbps191010Mbps100100 Spanning TreeOperations OnerootbridgepernetworkOnerootportpernonrootbridgeOnedesignatedportpersegment 碰撞域 x DesignatedPort F RootPort F DesignatedPort F NondesignatedPort B RootBridge NonrootBridge SWX SWY 100BaseT 10BaseT ASpanningTreeexample Spanning TreeOperations 1 选根网桥 每个网络中选择唯一一个根网桥 BridgeID最小的网桥当选 Spanning TreeOperations 1 Onerootbridgepernetwork RootBridge NonrootBridge SWX SWY 100BaseT 10BaseT SwitchXMAC0c0011111111DefaultPriority32768 SwitchYMAC0c0022222222DefaultPriority32768 Spanning TreeOperations 2 选根端口 对于每个非根网桥选择唯一一个根端口 比较非根网桥中每一个端口到根网桥的PathCost值 PathCost值最小的端口当选 Onerootportpernonrootbridge RootBridge NonrootBridge SWX SWY 100BaseT 10BaseT SwitchXMAC0c0011111111DefaultPriority32768 SwitchYMAC0c0022222222DefaultPriority32768 RootPort F Spanning TreeOperations 2 Spanning TreeOperations 3 选指定端口 在每个网段中选择唯一一个指定端口 比较该网段中每一个端口到根网桥的PathCost值 PathCost值最小的端口当选 Onedesignatedportpersegment RootBridge NonrootBridge SWX SWY 100BaseT 10BaseT SwitchXMAC0c0011111111DefaultPriority32768 SwitchYMAC0c0022222222DefaultPriority32768 RootPort F DesignatedPort F DesignatedPort F Spanning TreeOperations 3 TheotherportinBlockingstate RootBridge NonrootBridge SWX SWY 100BaseT 10BaseT SwitchXMAC0c0011111111DefaultPriority32768 SwitchYMAC0c0022222222DefaultPriority32768 RootPort F DesignatedPort F DesignatedPort F Spanning TreeOperations 4 x NondesignatedPort B Spanning TreePortStates Blocking阻塞 Noframesforwarded BPDUsheardListening Noframesforwarded listeningforframesLearning Noframesforwarded learningaddressesForwarding Framesforwarded learningaddressesDisabled Noframesforwarded noBPDUsheard Blocking 20Seconds Listening 15Seconds Learning 15Seconds Forwarding Spanning TreePortStates Spanning treetransitseachportthroughseveraldifferentstates Spanning TreeRecalculation SwitchYMAC0c0022222222DefaultPriority32768 SwitchXMAC0c0011111111DefaultPriority32768 Port0 Port1 Port0 Port1 10BaseT x 100BaseT RootBridge DesignatedPort RootPort F NondesignatedPort BLK DesignatedPort Spanning TreeRecalculation x DesignatedPort DesignatedPort RootBridge Spanning TreeRecalculation KeyIssue TimetoConvergence Convergenceoccurswhenalltheswitchandbridgeportshavetransitedtoeithertheforwardingortheblockingstate Whennetworktopologychanges switchesandbridgesmustrecomputetheSpanning TreeProtocol whichdisruptsusertraffic RapidSpanning TreeProtocol Thestandardandprotocolintroducethefollowing ClarificationofportstatesandrolesDefinitionofasetoflinktypesthatcangotoforwardingstaterapidlyAllowingswitches inaconvergednetwork togeneratetheirownBPDUsratherthanrelayingrootbridgeBPDUs TheRapidSpanningTreeProtocol IEEE802 1w willeventuallyreplacetheSpanningTreeProtocol IEEE802 1D RSTPPortStates RSTPPortState Discarding STPPortState Disabled Po