案例四 快速生成树解决环路问题.doc

案例四 快速生成树解决环路问题【背景描述】某学校为了开展计算机教学和网络办公，建立了一个计算机教室和一个校办公区，这两处的计算机网络通过两台交换机互连组成内部校园网，为了提高网络的可靠性，网络管理员用2条链路将交换机互连，现要在交换机上做适当的配置，使网络避免环路。【实现功能】使网络有冗余链路的情况下避免环路的产生，避免广播风暴等。【使用设备】设备类型设备名称设备数量交换机Switch2路由器三层交换机双绞线4计算机pc2【案例拓扑】【实现步骤】步骤1 交换机A的基本配置SwitchenSwitch#configure terminalSwitch(config)#hostname SwitchASwitchA(config)#vlan 10SwitchA(config-vlan)#name slaesSwitchA(config-vlan)#exitSwitchA(config)#interface fastEthernet 0/3SwitchA(config-if)#switchport access vlan 10SwitchA(config-if)#exitSwitchA(config)#interface range fastEthernet 0/1-2SwitchA(config-if-range)#switchport mode trunkSwitchA(config-if-range)#exit步骤2 交换机B的基本配置SwitchenSwitch#configure terminalSwitch(config)#hostname SwitchBSwitchB(config)#vlan 10SwitchB(config-vlan)#name slaesSwitchB(config-vlan)#exitSwitchB(config)#interface fastEthernet 0/3SwitchB(config-if)#switchport access vlan 10SwitchB(config-if)#exitSwitchB(config)#interface range fastEthernet 0/1-2SwitchB(config-if-range)#switchport mode trunkSwitchB(config-if-range)#exit步骤3 配置快速生成树协议SwitchA#configure terminal ！进入全局配置模式SwitchA(config)#spanning-tree ！开启生成树协议SwitchA(config)#spanning-tree mode rstp ！指定生成树协议类型为RSTPSwitchB#configure terminal ！进入全局配置模式SwitchB(config)#spanning-tree ！开启生成树协议SwitchB(config)#spanning-tree mode rstp ！指定生成树协议类型为RSTP验证测试：验证快速生成树协议已经开启SwitchA#show spanning-tree ！查看生成树的配置信StpVersion : RSTP ！生成树协议的版本SysStpStatus : Enabled ！生成树协议的运行状态，disable为关闭状态BaseNumPorts : 24MaxAge : 20HelloTime : 2ForwardDelay : 15BridgeMaxAge : 20BridgeHelloTime : 2BridgeForwardDelay : 15MaxHops : 20TxHoldCount : 3PathCostMethod : LongBPDUGuard : DisabledBPDUFilter : DisabledBridgeAddr : 00d0.f8bc.9835Priority : 32768 ！查看交换机的优先级TimeSinceTopologyChange : 0d:0h:1m:53sTopologyChanges : 0DesignatedRoot : 800000D0F8BC9835RootCost : 0 ！交换机到达根交换机的开销，0代表交换机为根RootPort : 0 ！查看交换机上的根端口，0代表交换机为根SwitchB#show spanning-tree ！查看交换机B生成树的配置信息StpVersion : RSTP ！生成树协议的版本SysStpStatus : EnabledBaseNumPorts : 24 ！生成树协议的运行状态，disable为关闭状态MaxAge : 20HelloTime : 2ForwardDelay : 15BridgeMaxAge : 20BridgeHelloTime : 2BridgeForwardDelay : 15MaxHops : 20TxHoldCount : 3PathCostMethod : LongBPDUGuard : DisabledBPDUFilter : DisabledBridgeAddr : 00d0.f8bf.fbbbPriority : 32768 ！查看交换机的优先级TimeSinceTopologyChange : 0d:0h:2m:34sTopologyChanges : 0DesignatedRoot : 800000D0F8BC9835RootCost : 200000 ！交换机到达根交换机的开销RootPort : Fa0/1 ！查看交换机上的根端口注：通过查看两台交换机的生成树信息发现，SwitchA为根交换机，SwitchB Fa0/1为根端口。步骤4.设置交换机的优先级，指定SwitchB为根交换机SwitchB(config)#spanning-tree priority 4096 !设置交换机优先级为4096SwitchB(config)#Z验证测试：验证交换机SwitchB的优先级SwitchB#show spanning-treeStpVersion : RSTPSysStpStatus : EnabledBaseNumPorts : 24MaxAge : 20HelloTime : 2ForwardDelay : 15BridgeMaxAge : 20BridgeHelloTime : 2BridgeForwardDelay : 15MaxHops : 20TxHoldCount : 3PathCostMethod : LongBPDUGuard : DisabledBPDUFilter : DisabledBridgeAddr : 00d0.f8bf.fbbbPriority : 4096 ！查看交换机的优先级TimeSinceTopologyChange : 0d:0h:17m:3sTopologyChanges : 0DesignatedRoot : 100000D0F8BFFBBBRootCost : 0RootPort : 0SwitchA#show spanning-tree ！查看交换机A生成树的配置信息StpVersion : RSTP ！生成树协议的版本SysStpStatus : Enabled ！生成树协议的运行状态，disable为关闭状态BaseNumPorts : 24MaxAge : 20HelloTime : 2ForwardDelay : 15BridgeMaxAge : 20BridgeHelloTime : 2BridgeForwardDelay : 15MaxHops : 20TxHoldCount : 3PathCostMethod : LongBPDUGuard : DisabledBPDUFilter : DisabledBridgeAddr : 00d0.f8bc.9835Priority : 32768 ！查看交换机的优先级TimeSinceTopologyChange : 0d:0h:17m:19sTopologyChanges : 0DesignatedRoot : 100000D0F8BFFBBBRootCost : 200000 ！交换机到达根交换机的开销，0代表交换机为根RootPort : Fa0/1 ！查看交换机上的根端口，0代表交换机为根验证测试：A.验证交换机SwitchA的端口1和端口2的状态。SwitchA#show spanning-tree interface fastEthernet 0/1 ！显示SwitchA端口fastEthernet 0/1的状态PortAdminPortfast : DisabledPortOperPortfast : DisabledPortAdminLinkType : autoPortOperLinkType : point-to-pointPortBPDUGuard: DisabledPortBPDUFilter: DisabledPortState : forwarding ！SwitchA的端口fastEthernet 0/1处于（forwarding）状态PortPriority : 128PortDesignatedRoot : 100000D0F8BFFBBBPortDesignatedCost : 0PortDesignatedBridge : 100000D0F8BFFBBBPortDesignatedPort : 8001PortForwardTransitions : 2PortAdminPathCost : 0PortOperPathCost : 200000PortRole : rootPort ！查看端口角色为根端口SwitchA#show spanning-tree interface fastEthernet 0/2 ！显示SwitchA端口fastEthernet 0/2的状态PortAdminPortfast : DisabledPortOperPortfast : DisabledPortAdminLinkType : autoPortOperLinkType : point-to-pointPortBPDUGuard: DisabledPortBPDUFilter: DisabledPortState : discarding ！SwitchA的端口fastEthernet 0/2处于（discarding）状态PortPriority : 128PortDesignatedRoot : 100000D0F8BFFBBBPortDesignatedCost : 0PortDesignatedBridge : 100000D0F8BFFBBBPortDesignatedPort : 8002PortForwardTransitions : 1PortAdminPathCost : 0PortOperPathCost : 200000PortRole : alternatePort ！SwitchA的F0/2端口为根端口的替换端口验证测试：B.如果SwitchB与SwitchA的端口F0/1之间的链路DOWN掉，验证交换机SwitchA的端口2的状态，并观察状态转发时间。SwitchA#show spanning-tree interface fastEthernet 0/2PortAdminPortfast : DisabledPortOperPortfast : DisabledPortAdminLinkType : autoPortOperLinkType : point-to-pointPortBPDUGuard: DisabledPortBPDUFilter: DisabledPortState : forwarding！SwitchA的端口fastEthernet 0/2从阻塞（discarding）状态转换到转发（forwarding）状态，说明生成树协议此时采用了原先处理阻塞状态的冗余链路状态转换时间大约2秒PortPriority : 128PortDesignatedRoot : 100000D0F8BFFBBBPortDesignatedCost : 0PortDesignatedBridge : 100000D0F8BFFBBBPortDesignatedPort : 8002PortForwardTransitions : 2PortAdminPathCost : 0PortOperPathCost : 200000PortRole : rootPort验证测试：C.如果SwitchB与SwitchA之间的一条链路DOWN掉（如拔掉网线），验证交换机PC1与PC2仍能互相ping 通，并观察ping 的丢包情况。以下为从PC1 ping PC2的结果（注：PC1的IP 地址为192.168.0.137，PC2的IP 地址为192.168.0.136）.C:Documents and SettingsAdministratorping 192.168.0.137Pinging 192.168.0.137 with 32 bytes of data:Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 timeping 192.168.0.137 -t ！从主机PC1 ping PC2(用连续ping ),然后拔掉SwitchB与SwitchA的端口F0/1之间的连线，观察丢包情况Pinging 192.168.0.137 with 32 bytes of data:Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Request timed out.Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64Reply from 192.168.0.137: bytes=32 time1ms TTL=64以上结果显示丢包数为一个。参考配置SwitchA#show run ！交换机SwitchA的全部配置System software version : 1.61(2) Build Aug 31 2005 ReleaseBuilding configura