快速生成树配置

导读	学校为了开展计算机教学和网络办公，建立的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联组成内部校园网，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配置，是网络避免环路。

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，在存在交换机环路的网络中生成一个没有环路的属性网络，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（快速生成树协议）、MSTP（多生成树协议）。生成树协议的特点收敛时间长。从主要链路出现故障到切换至备份链路需要 50 秒时间。快速生成树在生成树协议的基础上增加了两种端口角色，替换端口或备份端口，分别作为根端口和指定端口。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。

实验步骤

新建 packet tracer 拓扑图

默认情况下 STP 协议是启用的。通过两台交换机之间传送 BPDU 协议数据单元。
选出跟交换机、根端口等，以便确定端口的转发状态。图中标记为黄色的端口处于block 堵塞状态。
设置 RSTP。
查看交换机 show spanning-tree 状态，了解跟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 10 priority 4096 可以变化跟交换机的角色。
测试。当主链路处于 down 状态时候，能够自动的切换到备份链路，保证数据的正常转发。

实验设备

Switch_2960 2 台；PC 2 台；直连线（各设备互联）

PC1
IP: 192.168.1.2
Submask: 255.255.255.0
Gateway: 192.168.1.1

PC2
IP: 192.168.1.3
Submask: 255.255.255.0
Gateway: 192.168.1.1

S1
en
show spanning-tree
conf t
hostname S1
vlan 10
exit
int fa 0/10
switchport access vlan 10
exit
int range fa 0/1 - 2 #同时打开1号和2号端口，记得加range参数
switchport mode trunk #变成trunk模式，让多个vlan可以通讯
exit
spanning-tree mode rapid-pvst #定义为生成树协议
end

S2
en
conf t
hostname S2
vlan 10
exit
int fa 0/10
switchport access vlan 10
exit
int range fa 0/1 - 2 #同时打开1号和2号端口，记得加range参数
switchport mode trunk #变成trunk模式，让多个vlan可以通讯
exit
spanning-tree mode rapid-pvst #定义为生成树协议

end
show spanning-tree

PC1
ipconfig
ping -t 192.168.1.3

S2
en
conf t
int fa 0/1
shut
（查看 PC1 的 ping 情况是否正常）

实战演练

S1
Switch>en
Switch#show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address 0006.2A89.4544
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.BCCB.3D34
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Altn BLK 19 128.2 P2p
Fa0/10 Desg FWD 19 128.10 P2p

Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#hostname S1
S1(config)#vlan 10
S1(config-vlan)#exit
S1(config)#int fa 0/10
S1(config-if)#switchport access vlan 10
S1(config-if)#exit
S1(config)#int rang fa 0/1 - 2
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 rapid-pvst
S1(config)#end
S1#
%SYS-5-CONFIG_I: Configured from console by console

S1#
S1#show spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32769
Address 0006.2A89.4544
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.BCCB.3D34
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/1 Root FWD 19 128.1 P2p
Fa0/2 Altn BLK 19 128.2 P2p

VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 32778
Address 0006.2A89.4544
Cost 19
Port 1(FastEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
--More--


S2

Switch>en
Switch#conf t
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#hostname S2
S2(config)#vlan 10
S2(config-vlan)#exit
S2(config)#int fa 0/10
S2(config-if)#switchport access vlan 10
S2(config-if)#exit
S2(config)#int range fa 0/1-2
S2(config-if-range)#switchport mode trunk
S2(config-if-range)#exit
S2(config)#spanning-tree mode rapid-pvst
S2(config)#end
S2#
%SYS-5-CONFIG_I: Configured from console by console

S2#show spanning-tree
VLAN0001
Spanning tree enabled protocol rstp
Root ID Priority 32769
Address 0006.2A89.4544
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 0006.2A89.4544
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 20

Interface Role Sts Cost Prio.Nbr Type
---------------- ---- --- --------- -------- --------------------------------
Fa0/2 Desg FWD 19 128.2 P2p
Fa0/1 Desg FWD 19 128.1 P2p

VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 32778
Address 0006.2A89.4544
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 0006.2A89.4544
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
--More--

测试

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=65ms TTL=128
Reply from 192.168.1.3: bytes=32 time=16ms TTL=128
Reply from 192.168.1.3: bytes=32 time=19ms TTL=128
Reply from 192.168.1.3: bytes=32 time=13ms TTL=128
Reply from 192.168.1.3: bytes=32 time=17ms TTL=128
Reply from 192.168.1.3: bytes=32 time=16ms TTL=128
Reply from 192.168.1.3: bytes=32 time=17ms TTL=128
Reply from 192.168.1.3: bytes=32 time=18ms TTL=128
Reply from 192.168.1.3: bytes=32 time=19ms TTL=128
Reply from 192.168.1.3: bytes=32 time=18ms TTL=128
Reply from 192.168.1.3: bytes=32 time=16ms TTL=128
Reply from 192.168.1.3: bytes=32 time=16ms TTL=128
Reply from 192.168.1.3: bytes=32 time=18ms TTL=128

S2

S2#en
S2#conf t
Enter configuration commands, one per line. End with CNTL/Z.
S2(config)#int fa 0/1
S2(config-if)#shutdown

%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to administratively down

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to down

S2(config-if)#
S2(config-if)#no shutdown

%LINK-5-CHANGED: Interface FastEthernet0/1, changed state to up

%LINEPROTO-5-UPDOWN: Line protocol on Interface FastEthernet0/1, changed state to up

S2(config-if)#

本文原创地址：https://www.linuxprobe.com/quick-tree-configuration.html编辑：public，审核员：逄增宝

快速生成树配置

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