PVST+(每一個VLAN 的生成樹PVST 加)

PVST+(每一個VLAN 的生成樹PVST 加)

實驗拓撲：

 

分別在 SW1 和SW2 上show spanning-tree 查看結果：

SW1#show spanning-tree

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 0008.20ff.6400

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 0008.20ff.6400

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 15

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Desg FWD 19 128.23 P2p

Fa0/24 Desg FWD 19 128.24 P2p

SW2#show spanning-tree

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 0008.20ff.6400

Cost 19

Port 23 (FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Root FWD 19 128.23 P2p

Fa0/24 Altn BLK 19 128.24 P2p

注：以上拓撲中通過選舉最終SW1 爲根網橋，SW2 的F0/24 爲blocking 端口，也是就線路2 成爲了備

份鏈路。

分別在 SW1 和SW2 上建立VLAN2，VLAN3，VLAN4，按以下拓撲要求完成本實驗：

在 SW1 上建立VLAN2，VLAN3，VLAN4 並查看：

SW1(config)#vlan 2-4

SW1#show vlan

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4

Fa0/5, Fa0/6, Fa0/7, Fa0/8

Fa0/9, Fa0/10, Fa0/11, Fa0/12

Fa0/13, Fa0/14, Fa0/15, Fa0/16

Fa0/17, Fa0/18, Fa0/19, Fa0/20

Fa0/21, Fa0/22

2 VLAN0002 active

3 VLAN0003 active

4 VLAN0004 active

在 SW2 上建立VLAN2，VLAN3，VLAN4 並查看:

SW2(config)#vlan 2-4

SW2#show vlan

VLAN Name Status Ports

---- -------------------------------- --------- -------------------------------

1 default active Fa0/1, Fa0/2, Fa0/3, Fa0/4

Fa0/5, Fa0/6, Fa0/7, Fa0/8

Fa0/9, Fa0/10, Fa0/11, Fa0/12

Fa0/13, Fa0/14, Fa0/15, Fa0/16

Fa0/17, Fa0/18, Fa0/19, Fa0/20

Fa0/21, Fa0/22

2 VLAN0002 active

3 VLAN0003 active

4 VLAN0004 active

按以下拓撲要求完成本實驗：

要求：SW2 的VLAN1 和VLAN2 流量經過線路1 到達SW1 , SW2 的VLAN3 和VLAN4 的流量

通過線路2 到達SW1,當其中一條鏈路有問題走同一鏈路.

 

分別在 SW1 和SW2 上建立了VLAN2-4 後查看目前的生成樹狀態.

在SW1 上查看:

命令:show spanning-tree vlan 1

show spanning-tree vlan 2

show spanning-tree vlan 3

show spanning-tree vlan 4

SW1#show spanning-tree vlan 1

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 0008.20ff.6400

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 0008.20ff.6400

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Desg FWD 19 128.23 P2p

Fa0/24 Desg FWD 19 128.24 P2p

SW1#show spanning-tree vlan 2

VLAN0002

Spanning tree enabled protocol ieee

Root ID Priority 32770

Address 0008.20ff.6400

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)

Address 0008.20ff.6400

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Desg FWD 19 128.23 P2p

Fa0/24 Desg FWD 19 128.24 P2p

SW1#show spanning-tree vlan 3

VLAN0003

Spanning tree enabled protocol ieee

Root ID Priority 32771

Address 0008.20ff.6400

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32771 (priority 32768 sys-id-ext 3)

Address 0008.20ff.6400

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Desg FWD 19 128.23 P2p

Fa0/24 Desg FWD 19 128.24 P2p

SW1#show spanning-tree vlan 4

VLAN0004

Spanning tree enabled protocol ieee

Root ID Priority 32772

Address 0008.20ff.6400

This bridge is the root

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32772 (priority 32768 sys-id-ext 4)

Address 0008.20ff.6400

 

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Desg FWD 19 128.23 P2p

Fa0/24 Desg FWD 19 128.24 P2p

結果:查看生成樹狀態後發現針對VLAN1,VLAN2,VLAN3,VLAN3,SW1 都是扮演根網橋角

色.SW1 鏈接SW2 的兩個端口F0/23,F0/24 都是指定端口.

在SW2 上查看:

命令:show spanning-tree vlan 1

show spanning-tree vlan 2

show spanning-tree vlan 3

show spanning-tree vlan 4

SW2#show spanning-tree vlan 1

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 0008.20ff.6400

Cost 19

Port 23 (FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Root FWD 19 128.23 P2p

Fa0/24 Altn BLK 19 128.24 P2p

SW2#show spanning-tree vlan 2

VLAN0002

Spanning tree enabled protocol ieee

Root ID Priority 32770

Address 0008.20ff.6400

Cost 19

Port 23 (FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32770 (priority 32768 sys-id-ext 2)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Root FWD 19 128.23 P2p

Fa0/24 Altn BLK 19 128.24 P2p

SW2#show spanning-tree vlan 3

VLAN0003

Spanning tree enabled protocol ieee

Root ID Priority 32771

Address 0008.20ff.6400

Cost 19

Port 23 (FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32771 (priority 32768 sys-id-ext 3)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Root FWD 19 128.23 P2p

Fa0/24 Altn BLK 19 128.24 P2p

SW2#show spanning-tree vlan 4

VLAN0004

Spanning tree enabled protocol ieee

Root ID Priority 32772

Address 0008.20ff.6400

Cost 19

Port 23 (FastEthernet0/23)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32772 (priority 32768 sys-id-ext 4)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Root FWD 19 128.23 P2p

Fa0/24 Altn BLK 19 128.24 P2p

結果:查看生成樹狀態後發現針對VLAN1,VLAN2,VLAN3,VLAN3,SW2 都是扮演非根網橋角色,

SW2 的端口F0/24 都處在blocking 狀態.

問題所在：經過在SW1 和SW2 查看獲得的結果咱們來分析一下,如今SW1 的VLAN1 和VLAN2

是經過線路1 到達SW1 的,這符合本實驗的要求,但VLAN3,VLAN4 到SW1 走線路1 不符合本實驗的要

求,VLAN3,VLAN4 到SW1 要求走線路2.

分析:SW2 的VLAN3,VLAN4 到SW1 爲何走線路1 呢?由於SW2 相對於VLAN3,VLAN4 來講到

達SW1 F0/24 都是blocking 狀態,F0/23 爲轉發狀態,致使VLNA3,VLAN3 經過F0/23 走線路1 到達SW1.

解決方法:在SW2 上VLAN2,VLAN3 要到達SW1 只要SW2 的F0/23 爲blocking 狀態,F0/24 爲轉發

狀態,就達到本實驗的要求(SW2 的VLAN3,VLAN4 到SW1 走線路2)

之因此SW2 的F0/24 爲blocking 狀態,是由於相對於VLAN3,VLAN4 來講在經過生成樹決策的第4

步時,F0/23 端口號小於F0/23,小的優先，Lowest sender port ID 當兩臺交換機之間有兩條線路直連

時會用到這一項，<本實驗就是這樣>。經過以上分析,在SW2 上相對於VLAN3,VLAN4 來講,咱們能夠

更改參數,也就是在生成樹決策的第2 步就能夠作出決策，即便用Lowest path cost to root bridge

（到達根的最小路徑開銷）。

在SW2 上相對於VLAN3,VLAN4 更F0/24 到根(SW1)的花費,目前爲19,F0/23 到根也爲19,咱們更

改F0/24 端口到達SW1 的花費爲18 就能夠知足本實驗的要求.

在SW2 上配置如下命令:

SW2(config)#interface fastEthernet 0/24

SW2(config-if)#spanning-tree vlan 3-4 cost 18

查看更改的配置:

SW2#show run int f0/24

interface FastEthernet0/24

spanning-tree vlan 3-4 cost 18

end

作上以上配置後在SW2 上查看當前的VLAN3,VLAN4 的生成樹狀態:

SW2#show spanning-tree vlan 3

VLAN0003

Spanning tree enabled protocol ieee

Root ID Priority 32771

Address 0008.20ff.6400

Cost 18

Port 24 (FastEthernet0/24)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32771 (priority 32768 sys-id-ext 3)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Altn BLK 19 128.23 P2p

Fa0/24 Root FWD 18 128.24 P2p

SW2#show spanning-tree vlan 4

VLAN0004

Spanning tree enabled protocol ieee

Root ID Priority 32772

Address 0008.20ff.6400

Cost 18

Port 24 (FastEthernet0/24)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32772 (priority 32768 sys-id-ext 4)

Address 000d.bce7.5940

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 300

Interface Role Sts Cost Prio.Nbr Type

---------------- ---- --- --------- -------- --------------------------------

Fa0/23 Altn BLK 19 128.23 P2p

Fa0/24 Root FWD 18 128.24 P2p

經過命令show spanning-tree vlan 3 , show spanning-tree vlan 4 查看,咱們發現F0/23 爲blocking 狀

態,SW2 的VLAN3,VLAN4 到達SW1 的經過F0/24 到達,也就是走線路2,實如今本實驗的要求。最終線

路1,線路2 流量走勢圖: