spoto ccna vip课程录屏课件10-1stp生成树

1、STP生成树SPOTO CCNA VIP二层环路Server/host XRouter YSwitch A存在单点故障二层环路冗余拓扑冗余拓扑能够解决单点故障问题；冗余拓扑造成 广播风暴, 多帧复用, MAC地址不稳定的问题；Server/host XRouter YSegment 1Segment 2Switch ASwitch B二层环路广播风暴Host X发送广播帧；交换机继续没完没了的更新广播流量；Server/host XRouter YSegment 1Segment 2Switch ASwitch BBroadcast二层环路多帧复制Host X 发送一个单播数据帧给 Route

2、r Y；Router Y 的MAC地址还没有被每个交换机学习到；Router Y 接收2份相同的数据帧的拷贝；Server/host XRouter YSegment 1Segment 2Switch ASwitch Bunicast二层环路MAC表紊乱Host X 发送一个单播数据帧给 Router Y；Router Y 的MAC地址还没有被每个交换机学习到； Switches A and B 在Port1上学习到Host X的MAC地址；到达Router Y的数据帧被泛洪；Switches A and B 不正确的在Port2上学习到Host X的MAC地址；Server/host XRo

3、uter YSegment 1Segment 2Switch ASwitch Bunicast生成树的概念复杂的多环网络Server/hostWorkstationsLoopLoopLoop Broadcast生成树的概念采用生成树STP解决环路Spanning-Tree Protocol通过将特定的端口选为 Blocking state，来实现无环的拓扑；IEEE 802.1D 规定了这一行为；Cisco采用IEEE802.1D的增强的私有协议生成树PVST+;生成树的概念STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口每个段选择一个指定端口阻塞其他接口100BASE-T10BA

4、SE-T10BASE-TSW1SW2SW3ROOTRoot portRoot portDesignated portDesignated portDesignated port生成树的概念STP的操作每个广播域选择一个根桥BPDU (default = sent every 2 seconds)Root bridge = bridge with the lowest bridge IDBridge IDSwitch YDefault priority 32768 (8000 hex)MAC 0c Switch XDefault priority 32768 (8000 hex) MAC 0c

5、BPDU桥优先级2字节6字节桥MAC地址生成树的概念STP的操作BPDU生成树的概念STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP Designated portRP Root port根端口：具有最低根路径的接口要考虑的因素：1 最低的根桥ID2 最低的根路径代价3 最低发送者桥ID4 最低端口ID生成树的概念STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP Designated portRP Root po

6、rtRPRP生成树的概念STP路径开销Link SpeedCost (New IEEE Specification)Cost (Old IEEE Specification)10 Gb/s211 Gb/s41100 Mb/s191010 Mb/s100100最短路径是cost累加，而cost是基于链路的速率的。生成树的概念STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口每个段选择一个指定端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP Designated portRP Root portRPRPDPDP指定端口：具有最低根路径的接口要考虑的因素

7、：1 最低的根桥ID2 最低的根路径代价3 最低发送者桥ID4 最低端口ID生成树的概念STP的操作每个广播域选择一个根桥每个非根桥上选择一个根端口每个段选择一个指定端口阻塞其他端口100BASE-T10BASE-T10BASE-TSW1SW2SW3ROOTDP Designated portRP Root portRPRPDPDP生成树案例CASE1100 BASE-TSW1SW2SW3Pri 32768Mac 0C00.1111.0000ROOTDPPri 32768Mac 0C00.1111.1111Pri 32768Mac 0C00.1111.2222100 BASE-T100 BAS

8、E-TRPRP生成树案例CASE2100 BASE-TSW1SW2SW3Pri 32768Mac 0C00.1111.0000ROOTDPPri 32768Mac 0C00.1111.1111Pri 32768Mac 0C00.1111.222210 BASE-T100 BASE-TRPRPDPDP生成树案例CASE3Pri 32768Mac 0C00.1111.0000ROOTSW1SW4SW2SW3Pri 32768Mac 0C00.1111.1111Pri 32768Mac 0C00.1111.2222Pri 32768Mac 0C00.1111.3333RPRPRPDPDPDPDP生成

9、树案例CASE4Pri 32768Mac 0C00.1111.0000ROOTSW1SW2Pri 32768Mac 0C00.1111.2222RPDPDP生成树的概念STP的端口状态生成树的概念STP的端口状态In the blocking state, ports can only receive BPDUs. It may take up to 20 seconds to change from this state；In listening state, switches determine if there are any other paths to the root bridge. the forward delay and lasts for 15 seconds. In the listening state, user data is not being forwarded and MAC addresses are not being learned；In learning state user data is not forwarded, but MAC addresses are learned from any traffic that is seen. The learning state lasts for 15