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1、RSTP 的收敛过程1RSTP (IEEE 802.1w)RSTP与标准STP(IEEE 802.1D)的最主要区别是RSTP不再依赖转发延迟的计时器( Forward Delay timer)。RSTP通过Proposal/Agreement机制缩短收敛时间。根据RSTP的规则，如果连续三个BPDU丢失(默认6根据的规则，如果连续个丢失默认秒)，则认为交换机之间的RSTP关系中断。较短的失效时间便于更快的探测故障。标准STP有五个端口状态(Port State)，RSTP缩减为三个端口状态。为三个端口状态。2RSTP BPDU 3RSTP BPDU 标志位4RSTP BPDU 标志位Pl和D
2、i td tProposal 和Designa e porAgreement 和Root port5RSTP 端口状态6STP/RSTP收敛过程的三个步骤步骤1 选根桥步骤2 选根端口步骤3 选指定端口77RSTP Proposal/Agreement过程BID=32,768.0000.0C11.1111A所有交换机都运行RSTPPOST 未完成p14d i td tp2BPOST 已完成1. BPDU RID=BID of Cp4: des gna e por p6: designated portp4p3p51. BPDU RID=BID of BBID=32,768.0000.0C55.
3、5555BID of Proposalp6 port role: designated portno forwardingno learningp6BID of Proposalp4 port role: designated portno forwardingno learningCBID=32,768.0000.0C22.2222POST 已完成8RSTP Proposal/Agreement过程BID=32,768.0000.0C11.1111A所有交换机都运行RSTPPOST 未完成p1p2B3lt t tPOST 已完成BID=32,768.0000.0C55.5555p4p3p5你
4、的BID比我的小！我承认你是根。.p3: alterna e porp4: new root portp5: edge portp6: designated port2.sync(unchanged)2 (h d)p6C(g. sync(unchanged)Synchronization-同步BID=32,768.0000.0C22.2222POST 已完成9Root RSTP Proposal/Agreement过程BID=32,768.0000.0C11.1111A所有交换机都运行RSTPPOST 未完成p1p2B3lt t tPOST 已完成BID=32,768.0000.0C55.55
5、55p4p3p53. BPDU RID=BID of Cp3: alterna e porp4: new root portp5: edge portp6: designated portp6BID of Agreementp4 port role: root portforwardinglearningC当p6收到Agreement信息后，处于forwarding和learning状态。BID=32,768.0000.0C22.2222POST 已完成10Root RSTP Proposal/Agreement过程ABID=32,768.0000.0C11.1111p1: designate
6、d port2d i td t所有交换机都运行RSTPPOST 已完成p11. BPDU RID=BID of A Proposal1. BPDU RID=BID of CProposalp2: des gna e porp2Bp1 port role: designated portno forwardingno learningp2 port role: designated portno forwardingno learning4ttPOST 已完成p4p3p5p4: root porp6: designated portBID=32,768.0000.0C55.5555RPp6CDP
7、BID=32,768.0000.0C22.2222POST 已完成11Root RtRSTP Proposal/Agreement过程ABID=32,768.0000.0C11.1111p1: designated port2ttRoot 所有交换机都运行RSTPp13. BPDU RID=BID of AAgreementp2: new root por当p1收到Agreement信息后，处于forwarding和learning状态。p2Bp2 port role: root portforwardinglearning你的BID比当前的RID小！我承认你是根。.和p4p3p52.sync
8、(unchanged)2. sync (unchanged)2.sync(block)BID=32,768.0000.0C55.5555p3: alternate portp4: designated port p5: edge portp6C(g()DPpgp6: designated portBID=32,768.0000.0C22.222212RootRtRSTP Proposal/Agreement过程ABID=32,768.0000.0C11.1111p1: designated port2ttRoot 所有交换机都运行RSTPp1p2: root porp2Bp4p3p54 BPD
9、U RID=BID of ABID=32,768.0000.0C55.5555p3: alternate portp4: designated port p5: edge portp6C. of Proposalp4 port role: designated portno forwardingno learningpgp6: designated portBID=32,768.0000.0C22.222213RootRtRSTP Proposal/Agreement过程ABID=32,768.0000.0C11.1111p1: designated port2ttRoot 所有交换机都运行R
10、STPp1p2: root porp2Bp4p3p55. BPDU RID=BID of ABID=32,768.0000.0C55.5555p6CAgreement p6 port role: root portforwardinglearning你的RID比我的小！当p4收到Agreement信息后，处于forwarding和learning状态。p3: alternate portp4: designated port p5: edge portp6: new root portBID=32,768.0000.0C22.2222你的！我承认A是根。.14RtRSTP Proposal/A
11、greement过程ABID=32,768.0000.0C11.1111p1: designated port2ttRoot 所有交换机都运行RSTPp1p2: root porDPp2BRPp4p3p5BID=32,768.0000.0C55.5555DPp6CRPp3: alternate portp4: designated port p5: edge portp6: root portBID=32,768.0000.0C22.222215RtRSTP Proposal/Agreement过程ARoot p7: designated portp8: designated portp7BI
12、D=32,768.0000.0C11.1111所有交换机都运行RSTP1. BPDU RID=BID of DProposalp8 port role: designated portno forwardingNew linkp1p1: designated portp2: root portp3: alternate port1. BPDU RID=BID of A Plno learningp2Balternate p4: designated port p5: edge portp6: root portDp8Proposalp7 port role: designated portno
13、 forwardingno learningp4p3p5BID=32,768.0000.0C55.5555BID=32,768.0000.0C33.3333p6CCost = 19BID=32,768.0000.0C22.222216RtRSTP Proposal/Agreement过程ARoot BID=32,768.0000.0C11.1111p7所有交换机都运行RSTP当p7收到Agreement信息后，处于forwarding和learning状态2. BPDU RID=BID of D Agreementp8 port role: root portforwardingp1p1: d
14、esignated portp2: root portp3: alternate portp7: designated port和。learningp2Balternate p4: designated port p5: edge portp6: root portDp8p8: new root port你的BID比我的小！我承认你是根。.p4p3p5BID=32,768.0000.0C55.5555BID=32,768.0000.0C33.3333p6CCost = 19BID=32,768.0000.0C22.222217RtRSTP Proposal/Agreement过程ARoot D
15、PBID=32,768.0000.0C11.1111p7所有交换机都运行RSTPp1p1: designated portp2: root portp3: alternate portCost = 19p7: designated portp8: root portp2Balternate p4: designated port p5: edge portp6: root portDRPp8p4p3p5BID=32,768.0000.0C55.5555BID=32,768.0000.0C33.3333p6CCost = 19BID=32,768.0000.0C22.222218RtRSTP P
16、roposal/Agreement过程ARoot BID=32,768.0000.0C11.1111DPp7所有交换机都运行RSTPp1p1: designated portp2: root portp3: alternate portCost = 19Cost = 19p2Balternate p4: designated port p5: edge portp6: root portDRPp81. BPDU RID=BID of A Proposalp4p3p5BID=32,768.0000.0C55.5555BID=32,768.0000.0C33.3333p10p10 port role: designated portno forwardingno learningP
