網絡中原有兩臺交換機分別是SW1和SW2，由於公司業務發展網絡擴大將原來用於別處的交換機SW3接入到現有網絡中如圖3.1所示。按照圖中要求配置各交換機，其中SW1配置爲VTP的服務器模式，在SW1交換機上配置VLAN 2和VLAN 3，交換機SW2配置爲客戶機模式，使得SW2交換機能夠學習SW1交換機的VLAN信息。![]()
在配置完成後使用show vtp status命令和show vlan brief命令分別查看SW1和SW2的VTP信息和VLAN信息，如下所示：
SW1#show vtp status
VTP Version : 2
Configuration Revision : 2
Maximum VLANs supported locally : 1005
Number of existing VLANs : 7
VTP Operating Mode : Server
VTP Domain Name : benet
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x80 0x23 0xC0 0x22 0xD4 0xBC 0x68 0x64
Configuration last modified by 0.0.0.0 at 3-1-93 03:24:35
Local updater ID is 0.0.0.0 (no valid interface found)
SW1#show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active 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
Fa0/23, Gi0/1, Gi0/2
2 VLAN0002 active Fa0/1
3 VLAN0003 active Fa0/2
SW2#show vtp status
VTP Version : 2
Configuration Revision : 2
Maximum VLANs supported locally : 1005
Number of existing VLANs : 7
VTP Operating Mode : Client
VTP Domain Name : benet
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0x80 0x23 0xC0 0x22 0xD4 0xBC 0x68 0x64
Configuration last modified by 0.0.0.0 at 3-1-93 03:24:35
SW2#show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active 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
Fa0/23, Gi0/1, Gi0/2
2 VLAN0002 active Fa0/1
3 VLAN0003 active Fa0/2
新接入SW3交換機，在SW3通電後查看其VTP信息和VLAN信息。SW3交換機的VTP修訂號要高於SW1和SW2的修訂號並且域名也相同，並且在VLAN 數據庫中沒有VLAN 2和VLAN 3，如下：
SW3#show vtp status
VTP Version : 2
Configuration Revision : 15
Maximum VLANs supported locally : 255
Number of existing VLANs : 6
VTP Operating Mode : Client
VTP Domain Name : benet
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xD4 0xEA 0xC3 0x0A 0x97 0xC2 0x20 0xCF
Configuration last modified by 0.0.0.0 at 3-1-93 03:21:53
SW3#show vlan brief
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, Fa0/23, Fa0/24
Gi0/1, Gi0/2
4 VLAN0004 active
將SW2和SW3的物理鏈路連接好，配置連接端口爲TRUNK模式。由於新接入的SW3的VTP修訂號更高，所有SW1和SW2會使用SW3的VLAN數據庫覆蓋自身的數據庫。
接入SW3後，再次查看SW1和SW2的VTP和VLAN信息。
SW1的VTP和VLAN信息：
SW1#show vtp status
VTP Version : 2
Configuration Revision : 15
Maximum VLANs supported locally : 1005
Number of existing VLANs : 6
VTP Operating Mode : Server
VTP Domain Name : benet
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xD4 0xEA 0xC3 0x0A 0x97 0xC2 0x20 0xCF
Configuration last modified by 0.0.0.0 at 3-1-93 03:21:53
Local updater ID is 0.0.0.0 (no valid interface found)
SW1#show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active 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
Fa0/23, Gi0/1, Gi0/2
4 VLAN0004 active
SW2的VTP和VLAN信息：
SW2#show vtp status
VTP Version : 2
Configuration Revision : 15
Maximum VLANs supported locally : 1005
Number of existing VLANs : 6
VTP Operating Mode : Client
VTP Domain Name : benet
VTP Pruning Mode : Disabled
VTP V2 Mode : Disabled
VTP Traps Generation : Disabled
MD5 digest : 0xD4 0xEA 0xC3 0x0A 0x97 0xC2 0x20 0xCF
Configuration last modified by 0.0.0.0 at 3-1-93 03:21:53
SW2#show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active 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, Fa0/23
Gi0/1, Gi0/2
4 VLAN0004 active
由此可見，SW1和SW2已經使用VTP修訂號高的通告，並更新了自身的VLAN數據庫。
爲了避免上述現象的出現，在一個使用VTP的網絡中新加入交換機時應該將此交換機的VTP修訂號重置爲0，並將其更改爲透明模式。接入後在將其模式改爲相應的VTP模式。