STP(生成樹(shù)協(xié)議講解)

STP局域網(wǎng)中通常會(huì)存在冗余鏈路。需要一種方法阻塞冗余鏈路，消除路徑環(huán)路，并且在必要時(shí)將冗余鏈路自動(dòng)切換為轉(zhuǎn)發(fā)狀態(tài)，恢復(fù)網(wǎng)絡(luò)的連通性。生成樹(shù)協(xié)議就可以實(shí)現(xiàn)這樣的功能。生成樹(shù)協(xié)議包括STP、RSTP、MSTP等。本章對(duì)STP的工作原理進(jìn)行詳細(xì)介紹。引入了解STP消除環(huán)路的思想掌握STP的基本概念掌握STP計(jì)算過(guò)程掌握STP的端口狀態(tài)掌握STP拓?fù)涓淖兲幚磉^(guò)程了解STP的不足課程目標(biāo)學(xué)習(xí)完本課程，您應(yīng)該能夠：STP介紹STP基本概念STP計(jì)算過(guò)程STP端口狀態(tài)STP拓?fù)涓淖兲幚磉^(guò)程STP協(xié)議的不足目錄Page4交換機(jī)轉(zhuǎn)發(fā)流程回顧E0/2E0/3E0/5E0/600-0D-56-BF-88-1000-0D-56-BF-88-20PCASWASWBPCB123Page5環(huán)路引起的問(wèn)題之一——廣播風(fēng)暴PCASWASWB廣播12344Page6交換機(jī)學(xué)習(xí)MAC地址表回顧E0/2E0/3E0/5E0/600-0D-56-BF-88-1000-0D-56-BF-88-20PCASWASWBPCB123Page7E0/3E0/4E0/5E0/6PCASWASWB00-0D-56-BF-88-10E0/200-0D-56-BF-88-10E0/200-0D-56-BF-88-10E0/4錯(cuò)誤目的端口環(huán)路引起的問(wèn)題之二——MAC地址表不穩(wěn)定什么是STP？STP是二層網(wǎng)絡(luò)中用于消除環(huán)路的協(xié)議通過(guò)阻斷冗余鏈路來(lái)消除橋接網(wǎng)絡(luò)中可能存在的路徑回環(huán)當(dāng)前活動(dòng)路徑發(fā)生故障時(shí)，激活冗余備份鏈路，恢復(fù)網(wǎng)絡(luò)連通性ROOTPhysicalSegmentAPhysicalSegmentBPhysicalSegmentCPhysicalSegmentDPhysicalSegmentESTP消除環(huán)路的思想將網(wǎng)絡(luò)拓?fù)湫藜魹闃?shù)形選擇樹(shù)根節(jié)點(diǎn)確定最短路徑阻塞冗余鏈路ROOTPhysicalSegmentAPhysicalSegmentBPhysicalSegmentCPhysicalSegmentDPhysicalSegmentESTP介紹STP基本概念STP計(jì)算過(guò)程STP端口狀態(tài)STP拓?fù)涓淖兲幚磉^(guò)程STP協(xié)議的不足目錄橋和端口的角色橋的角色：根橋指定橋端口角色：根端口指定端口Alternate端口根橋根端口根端口指定端口指定端口指定端口Alternate端口指定橋SWASWBSWCSWA指定橋SWB橋ID橋ID用于在STP中唯一的標(biāo)識(shí)一個(gè)橋，橋ID由兩部分組成，長(zhǎng)度為8個(gè)字節(jié)橋優(yōu)先級(jí)：高16位(0~65535,默認(rèn)32768)優(yōu)先級(jí)（16bit）=4Bit橋優(yōu)先級(jí)+12Bit擴(kuò)展系統(tǒng)IDMAC地址：低48位橋優(yōu)先級(jí)橋MAC地址2字節(jié)6字節(jié)橋ID路徑開(kāi)銷（PathCost）路徑開(kāi)銷用于衡量橋與橋之間路徑的優(yōu)劣STP中每條鏈路都具有開(kāi)銷值路徑開(kāi)銷等于路徑上全部鏈路開(kāi)銷之和SWBSWCSWA1Gig1GigCost20Cost200100M鏈路開(kāi)銷標(biāo)準(zhǔn)配置BPDU網(wǎng)橋通過(guò)交互配置BPDU獲取STP計(jì)算所需要的參數(shù)配置BPDU基于二層組播方式發(fā)送，目的地址為01-80-C2-00-00-00配置BPDU由根橋周期發(fā)出，發(fā)送周期為HelloTime。配置BPDU老化時(shí)間為MaxAge。SWASWB配置BPDURootSWC配置BPDU配置BPDU格式DMA:目的MAC地址SMA:源MAC地址 L/T:幀長(zhǎng)LLCHeader:配置消息固定的鏈路頭Payload:BPDU數(shù)據(jù)PayloadL/TSMADMALLCHeaderRootIDRootPathCostBridgeIDPortIDParametersByteProtocolID2ProtocolVersionIDBPDUTypeFlagsMessageAge11184822MaxAgeHelloTimeForwardDelay222｝STP優(yōu)先級(jí)向量STP介紹STP基本概念STP計(jì)算過(guò)程STP端口狀態(tài)STP拓?fù)涓淖兲幚磉^(guò)程STP協(xié)議的不足目錄計(jì)算步驟任務(wù)一：選舉根橋任務(wù)二：確定端口角色SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACD1GigPathCost=201GigPathCost=20100MPathcost=200100MPathcost=200SWCBID=32768.MACC2Gig聚合Pathcost=18計(jì)算方法配置BPDU處理網(wǎng)橋?qū)⒏鱾€(gè)端口收到的配置BPDU和自己的配置BPDU做比較，得出優(yōu)先級(jí)最高的配置BPDU網(wǎng)橋用優(yōu)先級(jí)最高的配置BPDU更新本身的配置BPDU，用于選舉根橋和確定端口角色網(wǎng)橋從指定端口發(fā)送新的配置BPDU配置BPDU比較原則——優(yōu)先級(jí)向量最小者最優(yōu)首先比較RootBridgeID其次比較RootPathCost再次比較DesignateBridgeID再其次比較DesignatePortID最后比較BridgePortID根橋選舉過(guò)程SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC我是根橋我是根橋我是根橋我是根橋?qū)ふ易钚騃DRootID=8192.MACB根橋選舉過(guò)程（續(xù)）RootID=8192.MACBRootID=0.MACARootID=0.MACARootID=32768.MACCRootID=8192.MACBRootID=32768.MACCRootID=32768.MACCRootID=4096.MACDRootID=4096.MACDSWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACD根橋選舉過(guò)程（續(xù)）SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC我是根橋我是根橋SWA是根橋SWA是根橋根橋選舉過(guò)程（續(xù)）RootID=0.MACARootID=0.MACARootID=0.MACARootID=0.MACARootID=0.MACARootID=0.MACARootID=4096.MACDRootID=4096.MACDSWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACD根橋選舉結(jié)果SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC我是根橋SWA是根橋SWA是根橋SWA是根橋確定端口角色的標(biāo)準(zhǔn)根端口：網(wǎng)橋上到根橋最近的端口指定端口：端口的配置BPDU在其所屬鏈路上是最優(yōu)的Alternate端口：端口的配置BPDU在其所屬鏈路上不是最優(yōu)的，且端口不是根端口端口角色確定過(guò)程SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACD1GigPathCost=201GigPathCost=20100MPathcost=200100MPathcost=200SWCBID=32768.MACC2Gig聚合Pathcost=18RootID=32768.MACCRPC=0RootID=8192.MACBRPC=0端口角色確定過(guò)程（續(xù)）RootID=8192.MACBRPC=0RootID=8192.MACBRPC=0RootID=0.MACARPC=0RootID=0.MACARPC=0RootID=32768.MACCRPC=0RootID=32768.MACCRPC=0RootID=4096.MACDRPC=0RootID=4096.MACDRPC=0SWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACD端口角色確定過(guò)程（續(xù)）SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC我是根橋RPC=0我是根橋RPC=0SWA是根橋RPC=18RPC=200RPC=18SWA是根橋RPC=200端口角色確定過(guò)程（續(xù)）RootID=0.MACARPC=18RootID=0.MACARPC=200RootID=0.MACARPC=200RootID=0.MACARPC=0RootID=0.MACARPC=0RootID=0.MACARPC=18RootID=4096.MACDRPC=0RootID=4096.MACDRPC=0SWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACD端口角色確定過(guò)程（續(xù)）SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC我是根橋RPC=0SWA是根橋RPC=18RPC=38RPC=18RPC=218SWA是根橋RPC=38SWA是根橋RPC=218端口角色確定過(guò)程（續(xù)）RootID=0.MACARPC=18RootID=0.MACARPC=38RootID=0.MACARPC=0RootID=0.MACARPC=0RootID=0.MACARPC=18SWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACD端口角色確定過(guò)程（續(xù)）SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC我是根橋RPC=0SWA是根橋RPC=18RPC=38RPC=18RPC=58SWA是根橋RPC=38SWA是根橋RPC=58端口角色確定結(jié)果Alternate端口：端口既非根端口也非指定端口指定端口：端口擁有該鏈路上最優(yōu)的配置消息根橋路徑開(kāi)銷=38根橋ID=0.MACARootPathCost=18根橋ID=0.MACARootPathCost=38根橋ID=0.MACARootPathCost=0根端口：該端口到根橋的開(kāi)銷最小38<200根橋路徑開(kāi)銷=200SWBBID=8192.MACBSTP計(jì)算結(jié)果SWBBID=8192.MACBSWABID=0.MACASWDBID=4096.MACDSWCBID=32768.MACC指定端口指定端口根端口根端口根端口指定端口指定端口Alternate端口Alternate端口根橋指定端口等路徑開(kāi)銷計(jì)算根橋SWABID=0.MACASWABID=0.MACA根橋SWBBID=8192.MACBSWCBID=32768.MACCSWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACDPathcost=200Pathcost=200Pathcost=200Pathcost=200Pathcost=200Pathcost=200Pathcost=200DDRRDADDRRRDDA等路徑開(kāi)銷計(jì)算（續(xù)）RPathcost=200Pathcost=200SWABID=0.MACA根橋SWBBID=8192.MACBE0/1E0/2DDARPathcost=200Pathcost=200SWABID=0.MACA根橋SWBBID=8192.MACBE0/1DAPathcost=200E0/2E0/1E0/1E0/2PhysicalSegment收到低優(yōu)先級(jí)配置BPDU時(shí)的處理根橋根橋BPDUBPDUBPDUSWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCSWDBID=4096.MACDBPDU低優(yōu)先級(jí)配置BPDUHelloTimerBPDUSTP介紹STP基本概念STP計(jì)算過(guò)程STP端口狀態(tài)STP拓?fù)涓淖兲幚磉^(guò)程STP協(xié)議的不足目錄臨時(shí)環(huán)路問(wèn)題當(dāng)拓?fù)浣Y(jié)構(gòu)發(fā)生變化，新的配置BPDU要經(jīng)過(guò)一定的時(shí)延才能傳播到整個(gè)網(wǎng)絡(luò)，在所有網(wǎng)橋收到這個(gè)變化的消息之前可能會(huì)存在臨時(shí)環(huán)路根橋SWABID=0.MACASWBBID=8192.MACBSWCBID=4096.MACCDRDR根橋SWABID=0.MACASWBBID=8192.MACBSWCBID=4096.MACCDRDDRD新鏈路通過(guò)中間狀態(tài)避免臨時(shí)環(huán)路STP為端口定義了五種狀態(tài)：Disabled、Blocking、Listening、Learning、Forwarding各端口狀態(tài)對(duì)配置BPDU收發(fā)、MAC地址學(xué)習(xí)以及數(shù)據(jù)收發(fā)的處理有所不同F(xiàn)orwardDelay延時(shí)從中間狀態(tài)Listening經(jīng)過(guò)一個(gè)延時(shí)進(jìn)入另一個(gè)中間狀態(tài)Learning從Learning狀態(tài)再經(jīng)過(guò)一個(gè)延時(shí)進(jìn)入Forwarding狀態(tài)延時(shí)長(zhǎng)度為ForwardDelaySTP端口狀態(tài)機(jī)DisabledListeningBlockingForwardingLearning1）端口enabled2）端口disabled3）端口被選為根端口或指定端口4）端口被選為Alternate端口（阻塞）5）ForwardDelay延時(shí)（1）（2）（2）（2）（2）（1）（2）（4）（4）（5）（4）（5）（3）STP端口狀態(tài)示例SWBSWASWDSWCForwardingForwardingForwardingForwardingForwardingForwardingForwardingBlockingBlocking根橋ForwardingSTP介紹STP基本概念STP計(jì)算過(guò)程STP端口狀態(tài)STP拓?fù)涓淖兲幚磉^(guò)程STP協(xié)議的不足目錄E1/0/1拓?fù)浒l(fā)生變化HostAHostBROOTSWCSWASWBSWDSWE鏈路中斷E1/0/1E1/0/2E1/0/1E1/0/2E1/0/2E1/0/3E1/0/2E1/0/1E1/0/2E1/0/1從中斷到恢復(fù)需要等待MAC地址老化，將近5分鐘的時(shí)間！STP阻塞STP拓?fù)涓淖兲幚磉^(guò)程拓?fù)涓淖兿CN拓?fù)涓淖儜?yīng)答消息TCA拓?fù)涓淖冎梦坏腂PDUHostAHostBROOT鏈路中斷E1/0/1E1/0/2E1/0/1E1/0/2E1/0/1E1/0/2E1/0/3E1/0/2E1/0/1E1/0/2E1/0/1拓?fù)涓淖儠r(shí)網(wǎng)橋使用較小的MAC地址生存期從中斷到恢復(fù)最長(zhǎng)需要等待50秒的時(shí)間！12344555STP阻塞SWCSWASWBSWDSWETCNBPDUPayloadL/TSMADMALLCHeader網(wǎng)橋發(fā)送TCNBPDU的條件為有端口轉(zhuǎn)變?yōu)镕orwarding狀態(tài)，且該網(wǎng)橋至少包含一個(gè)指定端口有端口從Forwarding狀態(tài)或Learning狀態(tài)轉(zhuǎn)變?yōu)锽locking狀態(tài)ParametersByteProtocolID2ProtocolVersionIDBPDUType11TCA以及TC置位的配置BPDUPayloadL/TSMADMALLCHeader6543210TopologyChangeTopologyChangeAcknowledgment7標(biāo)志位置位第7位置位表示該消息為TCA第0位置位表示該消息為TC置位BPDU1到6位保留標(biāo)志位RootIDRootPathCostBridgeIDPortIDParametersByteProtocolID2ProtocolVersionIDBPDUTypeFlagsMessageAge11184822MaxAgeHelloTimeForwardDelay222拓?fù)涓淖兪諗繒r(shí)延分析SWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCDDRRDA根橋故障BPDU等待MaxAgeTimer鏈路中斷SWABID=0.MACASWBBID=8192.MACBSWCBID=32768.MACCDDRRDASWC根端口DOWNBPDUBPDUBPDU拓?fù)涓淖兪諗繒r(shí)延分析（續(xù)）ROOTSWCSWASWBSWDSWEE1/0/1E1/0/1E1/0/2E1/0/1E1/0/3E1/0/2E1/0/1E1/0/2E1/0/1E1/0/2新增鏈路或故障恢復(fù)鏈路新阻塞鏈路STP介紹STP基本概念STP計(jì)算過(guò)程STP端口狀態(tài)STP拓?fù)涓淖兲幚磉^(guò)程STP協(xié)議的不足目錄收斂時(shí)間長(zhǎng)PowerUpBlockingListeningLearningForwardingDisabledForwardDelayTimerForwardDelayTimer缺省情況下一個(gè)端口從Blocking狀態(tài)過(guò)渡到Forwarding狀態(tài)至少需要30秒鐘（兩倍的ForwardDelay）。對(duì)于一個(gè)拓?fù)洳环€(wěn)定網(wǎng)絡(luò)，會(huì)導(dǎo)致網(wǎng)絡(luò)的長(zhǎng)時(shí)間中斷拓?fù)渥兓諗繖C(jī)制不靈活ROOTSWCSWASWBSWDSWEE1/0/1E1/0/2E1/0/1E1/0/2E1/0/1E1/0/2E1/0/3E1/0/2E1/0/1E1/0/2E1/0/1STP阻塞主機(jī)頻繁上下線時(shí)，網(wǎng)絡(luò)會(huì)產(chǎn)生大量TCNPage54LANESWALANALANBLANCSWBSWCLANDRootLANC的指定端口E0/10E0/20E0/10E0/20E0/10E0/20STP基本配置－物理拓?fù)銹age55STP基本配置－配置命令LANESWALANALANBLANCSWBSWCLANDRootLANC的指定端口E0/10E0/20E0/10E0/20E0/10E0/20[Quidway]sysnameSWA[SWA]stpenable[SWA]stpmodestp[SWA]stppriority4096[Quidway]sysnameSWB[SWB]stpenable[SWB]stpmodestp[SWB]stppriority8192[Quidway]sysnameSWC[SWC]stpenable[SWC]stpmodestpE0/24Page56[SWC]displaystp[CISTGlobalInfo][ModeSTP]CISTBridge:32768.00e0-fc41-43b9BridgeTimes:Hello2sMaxAge20sFwDly15sMaxHop20CISTRoot/ERPC:4096.00e0-fc41-4259/20000CISTRegRoot/IRPC:32768.00e0-fc41-43b9/0CISTRootPortId:128.10BPDU-Protection:DisabledTCorTCNreceived:117TCcountperhello:1STPConvergeM