一、实验目标
- 理解生成树协议工作原理；
- 掌握快速生成树协议RSTP基本配置方法；
二、实验背景
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相连接组成内部校园网，为了提高网络的可靠性，作为网络管理员，你要用2条链路将交换机互连，现要求在交换机上做适当的配置，使网络避免环路。
三、技术原理
生成树协议(spanning-tree)，作用是在交换网络中提供冗余备份链路，并且解决交换网络中的环路问题；
生成树协议是利用SPA算法，在存在交换环路的网络中生成一个没有环路的树形网络。运用该算法将交换网络的冗余备份链路从逻辑上断开，当主链路出现故障时，能够自动的切换到备份链路，保证数据的正常转发；
生成树协议版本：STP、RSTP(快速生成树)、MSTP(多生成树协议)；
生成树协议的特点是收敛时间长，从主要链路出现故障到切换至备份链路需要50秒的时间；
快速生成树协议在生成树协议的基础上增加了两种端口角色：替换端口和备份端口，分别做为根端口和指定端口的冗余端口。当根端口或指定端口出现故障时，冗余端口不需要经过50秒的收敛时间，可以直接切换到替换端口或备份端口，从而实现RSTP协议小于1秒的快速收敛。
四、实验步骤
实验拓扑
默认情况下STP协议启用的，通过两台交换机之间传送BPDU协议数据单元，选出根交换机、根端口等，以便确定端口的转发状态。上图中标记为橙色的端口处于block堵塞状态。
设置RSTP
查看交换机 show spanning-tree 状态，了解根交换机和根端口情况；
通过更改交换机生成树的优先级spanning-tree vlan * priority 4096 可以变化根交换机的角色；
S1:
Switch>en Switch#conf t Enter configuration commands, one per line. End with CNTL/Z. Switch(config)#hostname S1 S1(config)#end S1# %SYS-5-CONFIG_I: Configured from console by console S1#show spanning-tree //查看交换机spanning-tree 状态 VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 0060.5C36.5620 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 0060.7078.8BDE Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Aging Time 20 Interface Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Fa0/10 Desg FWD 19 128.10 P2p Fa0/1 Root FWD 19 128.1 P2p Fa0/2 Altn BLK 19 128.2 P2p S1#conf t Enter configuration commands, one per line. End with CNTL/Z. S1(config)#interface fa0/10 S1(config-if)#switchport access vlan 10 //将fa0/10划分到vlan 10 % Access VLAN does not exist. Creating vlan 10 S1(config-if)#exit S1(config)#interface range fa0/1 - 2 //设置fa0/1,fa0/2端口状态为trunk模式 S1(config-if-range)#switchport mode trunk %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to down %LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up S1(config-if-range)#exit S1(config)#spanning-tree mode ? //设置spanning-tree 为RSTP模式 pvst Per-Vlan spanning tree mode rapid-pvst Per-Vlan rapid spanning tree mode S1(config)#spanning-tree mode rapid-pvst S1(config)#
S2:
Switch>en
Switch#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0060.5C36.5620
This bridge is the root //根交换机
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0060.5C36.5620
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/10 Desg FWD 19 128.10 P2p
Switch#
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/2, changed state to up
Switch#
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#hostname S2
S2(config)#interface fa0/10
S2(config-if)#switchport access vlan 10
% Access VLAN does not exist. Creating vlan 10
S2(config-if)#exit
S2(config)#interface range fa0/1 - 2
S2(config-if-range)#switchport mode trunk
S2(config-if-range)#exit
S2(config)#spanning-tree mode rapid-pvst
S2(config)#
五、测试
当主链路处于down状态时，能够自动的切换到备份链路，保证数据的正常转发。
在S2上shutdown 掉 fa0/1
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#int
Switch(config)#interface fa0/1
Switch(config-if)#shu
Switch(config-if)#shutdown //shutdown fa0/1端口
Switch(config-if)#
%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down
%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down
Switch#show spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32769
Address 0001.63E2.4A7A
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address 0001.63E2.4A7A
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p
VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 32778
Address 0001.63E2.4A7A
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 0001.63E2.4A7A
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20
Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Desg FWD 19 128.1 P2p
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/10 Desg FWD 19 128.10 P2p
Switch#
PC1:
PC>ipconfig
IP Address......................: 192.168.1.2
Subnet Mask.....................: 255.255.255.0
Default Gateway.................: 192.168.1.1
PC>ping -t 192.168.1.3
Pinging 192.168.1.3 with 32 bytes of data:
Reply from 192.168.1.3: bytes=32 time=78ms TTL=128
Reply from 192.168.1.3: bytes=32 time=94ms TTL=128
Reply from 192.168.1.3: bytes=32 time=78ms TTL=128
Reply from 192.168.1.3: bytes=32 time=78ms TTL=128
Reply from 192.168.1.3: bytes=32 time=78ms TTL=128
Reply from 192.168.1.3: bytes=32 time=94ms TTL=128
Reply from 192.168.1.3: bytes=32 time=93ms TTL=128
Reply from 192.168.1.3: bytes=32 time=93ms TTL=128
Reply from 192.168.1.3: bytes=32 time=62ms TTL=128
Reply from 192.168.1.3: bytes=32 time=94ms TTL=128
Reply from 192.168.1.3: bytes=32 time=79ms TTL=128
Reply from 192.168.1.3: bytes=32 time=94ms TTL=128
......
测试效果:
