生成树.docx

1、生成树BPDU 桥协议数据单元 2sBID、路径开销、端口ID、ROOT IDBID（桥ID）=设备优先级+MAC设备优先级：是一个数字，取值范围0-61440，交换机上默认是32768MAC：show version中间的Base ethernet MAC Address: 000D.BD24.EB8E路径开销cost：用来衡量当前设备到达根桥之间的距离，基于带宽。实际计算当前设备各个端口它到达根桥之间的路径开销之总和。端口ID=端口优先级+端口号端口优先级：是一个数字，取值范围0-240，各个端口默认是128ROOT ID=设备优先级+MAC表示当前网络里的树根那个设备的信息生成树的计算：

2、1 谁是根桥（ROOT）？（全网只有一个根桥）根桥的计算是比较Bridge ID，先比优先级，如果优先级一样，在比较MAC地址，取最小的谁最小谁就是我们的根桥。2 根端口 （各台交换机计算自己的根端口）流量转发端口路径开销：先比各个端口到达根桥的总路径开销，谁的路径开销小谁成为根端口相邻设备的BID：在比较于各个端接口相连设备的BID，谁连接的设备BID小，谁成为根端口。PORT ID：比较链路上各个端口的PORT ID，谁的小，谁成为我们的根端口。3 指定端口计算 （相对于流量的）流量转发端口路径开销：网络中可以帮忙转发流量的各个端口各自到达到根桥的总路径开销，取最小的 哪个端口的路径开销小

3、，哪个端口成为指定端口。BID：比较各端口所在设备的BID，哪个端口所在设备的BID小，哪个端口成为指定端口。端口ID：比较相连端口的端口ID，哪个端口的端口ID小，哪个端口成为指定端口。根桥设备的所有端口都是指定端口。查看根桥：ROOT#show spanning-tree vlan 1VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 0001.4359.3E50 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward

4、Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0001.4359.3E50 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 20Interface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/2 Desg FWD 19 128.2 P2pFa0/1 Desg FWD 19 128.1 P2p查看其他设备：Switch#show spanning-tree vlan 1VL

5、AN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 0001.4359.3E50 Cost 19 Port 1(FastEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 00D0.D358.A8DB Hello Time 2 sec Max Age 20 sec Forward Delay 15

6、 sec Aging Time 20Interface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/2 Desg FWD 19 128.2 ShrFa0/1 Root FWD 19 128.1 P2pFa0/3 Desg FWD 19 128.3 P2pFa0/5 Altn BLK 19 128.5 ShrFa0/4 Desg FWD 19 128.4 P2p公共生成树端口类型：根端口：具备流量转发能力指定端口：具备流量转发能力非指定端口（阻塞）：不能转发流量。如果在连续的20秒内没有接收到对端的BPDU，会自动向转发状态过渡（指定端口），会经历三个状态

7、的变化：监听（15秒）、学习（15秒）、转发。公共生成树的五个状态：侦听：15秒，发送和接受BPDU数据包，不会基于当前接口构建MAC地址表，但是不转发流量。（设备刚刚接入，阻塞端口连续20秒没有收到BPDU）学习：15秒，发送和接受BPDU数据包，准备进行流量转发，开始学习MAC地址转发：转发流量，发送和接受BPDU数据包,可以学习和维护CAM表阻塞：可以接收BPDU，最大维持20秒，20秒内每次接收到BPDU则计时器值恢复为0.禁用：不参与生成树公共生成树端口状态切换：测试一：阻塞端口转换到转发端口 测试设备SW3，我们关闭SW3上ROOT PORT直连链路，shutdown SW4的F0

8、/24SW3(config)#service timestamps debug datetime msec localtimeSW3#debug spanning-tree events Spanning Tree event debugging is onSW4(config)#int f0/24SW4(config-if)#shutdownSW4(config-if)#exitSW4(config)#SW3#*Mar 18 19:40:27.637: STP: VLAN0001 new root port Fa0/19, cost 38*Mar 18 19:40:27.637: STP:

9、VLAN0001 Fa0/19 - listening*Mar 18 19:40:29.637: STP: VLAN0001 sent Topology Change Notice on Fa0/19*Mar 18 19:40:42.637: STP: VLAN0001 Fa0/19 - learning*Mar 18 19:40:57.637: STP: VLAN0001 Fa0/19 - forwardingSW3# sh span vlan 1VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Addre

10、ss 000a.8a22.4400 Cost 38 Port 19 (FastEthernet0/19) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0011.bb66.1880 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300Interface Role Sts Cost Prio.Nbr Type- - - - - -F

11、a0/19 Root FWD 19 128.19 P2pF0/24接口恢复的日志：2w3d: %LINK-3-UPDOWN: Interface FastEthernet0/24, changed state to up*Mar 18 19:43:11.241: set portid: VLAN0001 Fa0/24: new port id 8018*Mar 18 19:43:11.241: STP: VLAN0001 Fa0/24 - listening*Mar 18 19:43:11.249: STP: VLAN0001 new root port Fa0/24, cost 38*Mar

12、 18 19:43:11.249: STP: VLAN0001 sent Topology Change Notice on Fa0/24*Mar 18 19:43:11.249: STP: VLAN0001 Fa0/19 - blocking2w3d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to up*Mar 18 19:43:26.241: STP: VLAN0001 Fa0/24 - learning*Mar 18 19:43:41.241: STP: VLAN000

13、1 Fa0/24 - forwardingSW3#结果：端口状态转换用时30秒优化：SW3(config)#spanning-tree uplinkfast*Mar 18 21:43:09.121: setting bridge id (which=1) prio 49153 prio cfg 49152 sysid 1 (on) id C001.0011.bb66.1880配置在各台设备上的，只对当前设备有效，打开uplinkfast之后，优先级变为49152，当前设备的cost自动向上+3000SW3#show spanning-tree vlan 1VLAN0001 Spanning t

14、ree enabled protocol ieee Root ID Priority 32769 Address 000a.8a22.4400 Cost 3038 Port 24 (FastEthernet0/24) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 49153 (priority 49152 sys-id-ext 1) Address 0011.bb66.1880 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging T

15、ime 300 Uplinkfast enabledInterface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/19 Altn BLK 3019 128.19 P2p Fa0/24 Root FWD 3019 128.24 P2p优化测试：SW4(config)#int f0/24SW4(config-if)#shutdownSW4(config-if)#exitSW4(config)#SW3#*Mar 18 21:47:40.837: STP: VLAN0001 new root port Fa0/19, cost 30382w3d: %SPANT

16、REE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/19 moved to Forwarding (UplinkFast). 2w3d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to down*Mar 18 21:47:42.837: STP: VLAN0001 sent Topology Change Notice on Fa0/19 2w3d: %LINK-3-UPDOWN: Interface FastEthernet0

17、/24, changed state to down SW3#SW3#sh span vl 1VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 000a.8a22.4400 Cost 3038 Port 19 (FastEthernet0/19) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 49153 (priority 49152 sys-id-ext 1) Address 0011.bb66

18、.1880 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15 Uplinkfast enabledInterface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/19 Root FWD 3019 128.19 P2pSW3 F0/24端口恢复的过程2w3d: %LINK-3-UPDOWN: Interface FastEthernet0/24, changed state to up*Mar 18 21:49:49.773: set portid: VLAN0001 Fa

19、0/24: new port id 8018*Mar 18 21:49:49.773: STP: VLAN0001 Fa0/24 - listening2w3d: %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/24, changed state to up*Mar 18 21:49:51.157: STP: VLAN0001 Fa0/24: root port delay timer active*Mar 18 21:49:51.157: STP: VLAN0001 Fa0/24 - blockingSW3#SW3#

20、sh span vl 1VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 000a.8a22.4400 Cost 3038 Port 19 (FastEthernet0/19) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 49153 (priority 49152 sys-id-ext 1) Address 0011.bb66.1880 Hello Time 2 sec Max Age 20 s

21、ec Forward Delay 15 sec Aging Time 15 Uplinkfast enabledInterface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/19 Root FWD 3019 128.19 P2p Fa0/24 Altn BLK 3019 128.24 P2p SW3#*Mar 18 21:50:26.157: STP: VLAN0001 new root port Fa0/24, cost 3038*Mar 18 21:50:26.157: STP: VLAN0001 Fa0/19 - blocking (uplink

22、fast)2w3d: %SPANTREE_FAST-7-PORT_FWD_UPLINK: VLAN0001 FastEthernet0/24 moved to Forwarding (UplinkFast).*Mar 18 21:50:26.157: STP: VLAN0001 sent Topology Change Notice on Fa0/24SW3#SW3#sh span vl 1VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 000a.8a22.4400 Cost 3038 Po

23、rt 24 (FastEthernet0/24) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 49153 (priority 49152 sys-id-ext 1) Address 0011.bb66.1880 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 15 Uplinkfast enabledInterface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/19 Altn

24、 BLK 3019 128.19 P2p Fa0/24 Root FWD 3019 128.24 P2p测试二：阻塞端口转换到转发端口 测试设备SW3，我们关闭SW3上ROOT PORT相关的非直连链路，shutdown SW2的F0/19SW3# sh span vlan 1 VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 000a.8a22.4400 Cost 38 Port 24 (FastEthernet0/24) Hello Time 2 sec Max Age 20 sec Fo

25、rward Delay 15 sec Bridge ID Priority 32769 (priority 32768 sys-id-ext 1) Address 0011.bb66.1880 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 300Interface Role Sts Cost Prio.Nbr Type- - - - - -Fa0/19 Altn BLK 19 128.19 P2p Fa0/24 Root FWD 19 128.24 P2pSW2(config)#int f0/19SW2(conf

26、ig-if)#shutdownSW3# *Mar 18 19:46:02.413: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:04.409: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:06.409: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:08.409: STP: VLAN0001 heard root 32

27、769-000e.d785.5300 on Fa0/24*Mar 18 19:46:10.409: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:12.409: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:14.409: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:16.409: STP: VLAN0001 heard

28、 root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:18.409: STP: VLAN0001 heard root 32769-000e.d785.5300 on Fa0/24*Mar 18 19:46:20.245: STP: VLAN0001 new root port Fa0/19, cost 38*Mar 18 19:46:20.245: STP: VLAN0001 Fa0/19 - listening*Mar 18 19:46:20.409: STP: VLAN0001 heard root 32769-000e.d785.5300

29、on Fa0/24*Mar 18 19:46:20.409: STP: VLAN0001 Topology Change rcvd on Fa0/24*Mar 18 19:46:20.409: STP: VLAN0001 sent Topology Change Notice on Fa0/19 *Mar 18 19:46:35.245: STP: VLAN0001 Fa0/19 - learning*Mar 18 19:46:50.245: STP: VLAN0001 sent Topology Change Notice on Fa0/19*Mar 18 19:46:50.245: STP: VLAN0001 Fa0/19 - forwarding结果：端口状态转换用时50秒SW3#show spanning-tree vlSW3#show spanning-tree vlan 1VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 000a.8a22.4400 Cost 38 Port 19 (FastEthernet0/19) Hel