一、實驗目標
- 理解生成樹協議工作原理；
- 掌握快速生成樹協議RSTP基本配置方法；
二、實驗背景
學校為了開展計算機教學和網絡辦公，建立了一個計算機教室和一個校辦公區，這兩處的計算機網絡通過兩台交換機互相連接組成內部校園網，為了提高網絡的可靠性，作為網絡管理員，你要用2條鏈路將交換機互連，現要求在交換機上做適當的配置，使網絡避免環路。
三、技術原理
生成樹協議(spanning-tree)，作用是在交換網絡中提供冗余備份鏈路，並且解決交換網絡中的環路問題；
生成樹協議是利用SPA算法，在存在交換環路的網絡中生成一個沒有環路的樹形網絡。運用該算法將交換網絡的冗余備份鏈路從邏輯上斷開，當主鏈路出現故障時，能夠自動的切換到備份鏈路，保證數據的正常轉發；
生成樹協議版本：STP、RSTP(快速生成樹)、MSTP(多生成樹協議)；
生成樹協議的特點是收斂時間長，從主要鏈路出現故障到切換至備份鏈路需要50秒的時間；
快速生成樹協議在生成樹協議的基礎上增加了兩種端口角色：替換端口和備份端口，分別做為根端口和指定端口的冗余端口。當根端口或指定端口出現故障時，冗余端口不需要經過50秒的收斂時間，可以直接切換到替換端口或備份端口，從而實現RSTP協議小於1秒的快速收斂。
四、實驗步驟
實驗拓撲
默認情況下STP協議啟用的，通過兩台交換機之間傳送BPDU協議數據單元，選出根交換機、根端口等，以便確定端口的轉發狀態。上圖中標記為橙色的端口處於block堵塞狀態。
設置RSTP
查看交換機 show spanning-tree 狀態，了解根交換機和根端口情況；
通過更改交換機生成樹的優先級spanning-tree vlan * priority 4096 可以變化根交換機的角色；
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 //查看交換機spanning-tree 狀態 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 //將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 //設置fa0/1,fa0/2端口狀態為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 ? //設置spanning-tree 為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 //根交換機
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、測試
當主鏈路處於down狀態時，能夠自動的切換到備份鏈路，保證數據的正常轉發。
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
......
測試效果:
