2023学年完整公开课版STP

《HCIA-R&S华为网络认证》STP原理与配置课程团队：叶礼兵张悦吴伟强目录环路引起的问题STP的原理STP的拓扑变化STP的配置学完本课程后，您应该能够：掌握STP的工作原理掌握STP的基本配置为了提高网络可靠性，交换网络中通常会使用冗余链路。然而，冗余链路会给交换网络带来环路风险，并导致广播风暴以及MAC地址表不稳定等问题，进而会影响到用户的通信质量。生成树协议STP（SpanningTreeProtocol）可以在提高可靠性的同时又能避免环路带来的各种问题。前言二层交换网络交换机之间通过多条链路互连时，虽然能够提升网络可靠性，但同时也会带来环路问题。SWASWBSWDSWCSWE广播风暴

环路会引起广播风暴。网络中的主机会收到重复数据帧。00-05-06-07-08-AA00-05-06-07-08-BBSWBSWASWC主机A主机BMAC地址表震荡

环路会引起MAC地址表震荡。MAC端口00-05-06-07-08-AAG0/0/300-05-06-07-08-AAG0/0/2主机A主机BSWASWCSWBG0/0/2G0/0/1G0/0/3G0/0/1G0/0/2G0/0/1G0/0/2G0/0/300-05-06-07-08-AA00-05-06-07-08-BBMAC地址表STP通过阻塞端口来消除环路，并能够实现链路备份的目的。STP的作用SWASWCSWBSTP操作选举一个根桥。每个非根交换机选举一个根端口。每个网段选举一个指定端口。阻塞非根、非指定端口。Non-RootNon-RootDARRDDSWASWCSWBRootPage10根桥选举

每一台交换机启动STP后，都认为自己是根桥。SWA3276800-01-02-03-04-BB3276800-01-02-03-04-CC409600-01-02-03-04-AASWCSWBRootPage11根端口选举

非根交换机在选举根端口时分别依据该端口的根路径开销、对端BID、对端PID和本端PID。RootG0/0/1G0/0/2G0/0/1G0/0/2G0/0/2G0/0/1RRSWASWCSWBRPC20000RPC0RPC0RPC200003276800-01-02-03-04-BB3276800-01-02-03-04-CC409600-01-02-03-04-AAPage12指定端口选举

非根交换机在选举指定端口时分别依据根路径开销、BID、PID。未被选举为根端口或指定端口的端口为预备端口，将会被阻塞。RootG0/0/1G0/0/2G0/0/1G0/0/2G0/0/2G0/0/1ADDDSWASWCSWB3276800-01-02-03-04-BB3276800-01-02-03-04-CC409600-01-02-03-04-AARRRPC20000RPC0RPC0RPC20000Page13端口状态转换1端口初始化或使能;2端口被选为根端口或指定端口。3端口不再是根端口或指定端口。4forwarddelay计时器超时。5端口禁用或链路失效。LearningDisabledForwarding1Blocking3343455552ListeningPage14BPDUBPDU包含桥ID、路径开销、端口ID、计时器等参数。PIDPVIBPDUTypeFlagsRootIDRPCBridgeIDPortIDMessageAgeMaxAgeHelloTimeFwdDelayBPDUBPDURootSWASWBSWCBPDUPage15计时器配置BPDU报文每经过一个交换机，MessageAge都加1。如果MessageAge大于MaxAge，非根桥会丢弃该配置BPDU。BPDU间隔(2秒)MSGAge:0MaxAge:20MSGAge:1MaxAge:20MSGAge:2MaxAge:20MSGAge:2MaxAge:20MSGAge:1MaxAge:20SWASWBSWCSWDSWEPage16根桥故障非根桥会在BPDU老化之后开始根桥的重新选举。RootSWASWBBPDUSWCBPDUPage17直连链路故障SWB检测到直连链路物理故障后，会将预备端口转换为根端口。SWB新的根端口会在30秒后恢复到转发状态。Page17SWASWBRootADDRDRSWCADPage18非直连链路故障非直连链路故障后，SWC的预备端口恢复到转发状态大约需要50秒。SWAASWCRootBPDUBPDUSWBBPDUPage19拓扑改变导致MAC地址表错误MAC地址表项的默认老化时间是300秒。在这段时间内，SWB无法将数据从G0/0/2端口转发给主机B。MAC端口00-05-06-07-08-AAG0/0/300-05-06-07-08-BBG0/0/1主机A主机BSWASWCSWBG0/0/2G0/0/1G0/0/3G0/0/1G0/0/2G0/0/1G0/0/200-05-06-07-08-AA00-05-06-07-08-BBMAC地址表Page20拓扑改变导致MAC地址表变化MAC端口00-05-06-07-08-AAG0/0/300-05-06-07-08-BBG0/0/100-05-06-07-08-BBG0/0/2主机A主机BSWASWCSWBG0/0/2G0/0/1G0/0/3G0/0/1G0/0/2G0/0/1G0/0/200-05-06-07-08-AA00-05-06-07-08-BB5.TC1.TCN2.TCA3.TCN4.TCMAC地址表Page21STP模式SWBSWCSWA[SWA]stpmode?

mstpMultipleSpanningTreeProtocol(MSTP)mode

rstpRapidSpanningTreeProtocol(RSTP)mode

stpSpanningTreeProtocol(STP)mode[SWA]stpmodestpPage22配置交换机优先级通过修改交换机的优先级，可以配置交换机为根交换机。409600-01-02-03-04-AASWBSWCSWA[SWA]stppriority4096Apr15201616:15:33-08:00SWADS/4/DATASYNC_CFGCHANGE:OID1.3.6.1.4.1.2011.5.25.191.3.1configurationshavebeenchanged.Thecurrentchangenumberis4,thechangeloopcountis0,andthemaximumnumberofrecordsis4095.Page23配置路径开销SWBSWCSWA[SWA]stppathcost-standard?

dot1d-1998IEEE802.1D-1998

dot1tIEEE802.1T

legacyLegacy[SWA]interfaceGigabitEthernet0/0/1

[SWA-GigabitEthernet0/0/1]stpcost2000G0/0/1Page24配置验证[SWA]displaystp[CISTGlobalInfo][ModeSTP]CISTBridge:4096.00-01-02-03-04-BBBridgeTimes:Hello2sMaxAge20sFwDly15sMaxHop20CISTRoot/ERPC:4096.00-01-02-03-04-BB/0CISTRegRoot/IRPC:4096.00-01-02-03-04-BB/0CISTRootPortId:0.0BPDU-Protection:DisabledTCorTCNreceived:37TCcountperhello:0STPConvergeMode:NormalShareregion-configuration:EnabledTimesincelastTC:0days0h:1m:29s……Page25配置验证[SWA]displaystp……[Port1(GigabitEthernet0/0/1)][FORWARDING]PortProtocol :EnabledPortRole :DesignatedPortPortPriority :128PortCost(Dot1T) :Config=2000/Active=2000DesignatedBridge/Port :4096.00-01-02-03-04-BB/128.1PortEdged :Config=default/Active=