网络基本情况
网络拓扑结构为:中心交换机采用Cisco Catalyst 4006-S3，Supervisor Engine III G引擎位于第1插槽，用于实现三层交换;1块24口1000Base-T模块位于第2插槽，用于连接网络服务器;1块6端口1000Base-X模块位于第3插槽，用于连接6台骨干交换机。
所有服务器划分为一个VLAN，即VLAN 50。四台Catalyst 2950G-24-SMI交换机也只划分为一个VLAN，分别为VLAN 60、VLAN 70、VLAN 80和VLAN 90。
Catalyst 3550-24-EMI划分为4个VLAN，分别为VLAN 10、VLAN 20、VLAN 30和VLAN 40。Catalyst 3550-24-SMI划分2个VLAN，分别为VLAN 60和VLAN 80，与另外两台Catalyst 2950G-24-SMI交换机分别位于同一VLAN。
实例分析
由于所有Catalyst 2950G交换机都是一个独立的VLAN，因此，必须先在这些交换机上创建VLAN(VLAN 60~VLAN 90)，并将所有端口都指定至该VLAN。然后，再在Catalyst 4006交换机相应端口上分别创建VLAN。Catalyst 4006的1000Base-X端口分别与各Catalyst 2950G的1000Base-X端口连接。其中，GigabitEthernet3/2端口连接至1号Catalyst 2950交换机(VLAN 60)，GigabitEthernet3/3端口连接至2号Catalyst 2950交换机(VLAN 70)，GigabitEthernet3/4端口连接至3号Catalyst 2950交换机(VLAN 80)，GigabitEthernet3/5端口连接至4号Catalyst 2950交换机(VLAN 90)，GigabitEthernet3/6端口连接至6号楼交换机(VLAN 80)。
由于在Catalyst 3550-24-EMI上划分有4个VLAN(VLAN 10～VLAN 40)，而4个VLAN都需借助于一条1000Base-X链路实现与Catalyst 4006的GigabitEthernet3/1端口连接，因此，必须在Catalyst 4006与Catalyst 3550-24- EMI之间创建一个Trunk。
同样，在Catalyst 3550-24-SMI上划分有2个VLAN(VLAN 60和VLAN 80)，而4个VLAN都需借助于一条1000Base-X链路实现与Catalyst 4006的GigabitEthernet3/6端口连接，因此，必须在Catalyst 4006与Catalyst 3550-24- EMI之间创建一个Trunk。
另外，所有服务器均连接至Catalyst 4006的1000Base-T模块，并单独成为一个VLAN(VLAN 90)，因此，也必须为这些交换机创建一个VLAN，并将所有端口指定至该VLAN。需要注重的是，考虑到网络治理的需要，也可以剩余几个RJ-45端口(如21至24端口)不指定至任何VLAN，从而便于连接网络治理设备。默认状态下，所有端口都属于VLAN1，而且也只有在VLAN1中才能实现对网络中所有设备的治理。
配置清单
●Cisco Catalyst 4006交换机配置清单
Current configuration : 5594 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service passWord-encryption
service compress-config
!
hostname hsnc
!
boot system bootflash:cat4000-is-mz.121-8a.EW1.bin
no logging console
enable secret level 1 5 $1$rkQW$1HKyKdN5f.Ri5zxeoF8Yv/
!
ip subnet-zero
!
!
!
interface GigabitEthernet1/1
no snmp trap link-status
!--不为Supervisor Engine III G引擎中的1000Base-X插槽指定VLAN
interface GigabitEthernet1/2
no snmp trap link-status
!
!
interface GigabitEthernet2/1
switchport Access vlan 50
no snmp trap link-status
!--将端口GigabitEthernet2/1指定至VLAN 50
!
interface GigabitEthernet2/2
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/3
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/4
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/5
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/6
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/7
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/8
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/9
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/10
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/11
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/12
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/13
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/14
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/15
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/16
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/17
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/18
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/19
switchport access vlan 50
no snmp trap link-status
!
interface GigabitEthernet2/20
switchport access vlan 50
no snmp trap link-status
!--不将GigabitEthernet2/20～24指定至任何VLAN
!
interface GigabitEthernet3/1
switchport trunk encapsulation dot1q
！--启用802.1Q Trunk封装协议，即在该端口创建Trunk switchport trunk allowed vlan 1-80
！--答应vlan 1-90在该中继线通讯
！--可以拒绝或答应某个VLAN访问该Trunk
！--确保未被授权的VLAN通过该Trunk，实现VLAN的访问安全 switchport mode trunk
！--将该端口设置为Trunk
description netcenter
no snmp trap link-status
!
interface GigabitEthernet3/2
switchport access vlan 60
no snmp trap link-status
!--将端口GigabitEthernet3/2指定至VLAN 60
!
interface GigabitEthernet3/3
switchport access vlan 70
no snmp trap link-status
!--将端口GigabitEthernet3/3指定至VLAN 70
!
interface GigabitEthernet3/4
switchport access vlan 80
no snmp trap link-status
!--将端口GigabitEthernet3/4指定至VLAN 80
!
interface GigabitEthernet3/5
switchport access vlan 90
no snmp trap link-status
!--将端口GigabitEthernet3/5指定至VLAN 90
!
interface GigabitEthernet3/6
switchport trunk encapsulation dot1q
！--启用802.1Q Trunk封装协议，即在该端口创建Trunk
switchport trunk allowed vlan 1-80
！--答应vlan 1-90在该中继线通讯
！--可以拒绝或答应某个VLAN访问该Trunk
！--从而确保未被授权的VLAN通过该Trunk，实现VLAN访问安全
switchport mode trunk
！--将该端口设置为Trunk
description netcenter
no snmp trap link-status
!
interface Vlan1
description netmanger
no ip address
!
!--对VLAN1进行描述
interface Vlan10
description network center
no ip address
!--对VLAN2进行描述
!
interface Vlan20
description computer center
no ip address
!
interface Vlan30
description network lab
no ip address
!
interface Vlan40
description huaxuelou
no ip address
!
interface Vlan50
description wulilou
no ip address
!
interface Vlan60
description shengwulou
no ip address
!
interface Vlan70
description zhongwenxi
no ip address
!
interface Vlan80
description tushuguan
no ip address
!
!
line con 0
stopbits 1
line vty 0 4
password aaa
login
!
end
●Cisco Catalyst 3550-EMI配置清单
Building configuration...
Current configuration : 4055 bytes
!
version 12.1
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname Office
!
enable secret 5 $1$p0fU$JeyPOM0RuL.Fqfe71efHF1
!
ip subnet-zero
!
!
spanning-tree extend system-id
!
!
!
interface FastEthernet0/1
switchport access vlan 10
!--将端口FastEthernet0/1指定至VLAN 10
no ip address
!
interface FastEthernet0/2
switchport access vlan 10
no ip address
!
interface FastEthernet0/3
switchport access vlan 10
no ip address
!
interface FastEthernet0/4
switchport access vlan 10
no ip address
!
interface FastEthernet0/5
switchport access vlan 10
no ip address
!
interface FastEthernet0/6
switchport access vlan 20
no ip address
!--将端口FastEthernet0/6指定至VLAN 20
!
interface FastEthernet0/7
switchport access vlan 20
no ip address
!
interface FastEthernet0/8
switchport access vlan 20
no ip address
!
interface FastEthernet0/9
switchport access vlan 20
no ip address
!
interface FastEthernet0/10
switchport access vlan 20
no ip address
!
interface FastEthernet0/11
switchport access vlan 30
no ip address
!--将端口FastEthernet0/6指定至VLAN 30
!
interface FastEthernet0/12
switchport access vlan 30
no ip address
!
interface FastEthernet0/13
switchport access vlan 30
no ip address
!
interface FastEthernet0/14
switchport access vlan 30
no ip address
!
interface FastEthernet0/15
switchport access vlan 30
no ip address
!
interface FastEthernet0/16
switchport access vlan 30
no ip address
!
interface FastEthernet0/17
switchport access vlan 30
no ip address
!
interface FastEthernet0/18
switchport access vlan 30
no ip address
!
interface FastEthernet0/19
switchport access vlan 40
no ip address
!--将端口FastEthernet0/6指定至VLAN 40
!
interface FastEthernet0/20
switchport access vlan 40
no ip address
!
interface FastEthernet0/21
switchport access vlan 40
no ip address
!
interface FastEthernet0/22
switchport access vlan 30
no ip address
!
interface FastEthernet0/23
switchport access vlan 40
no ip address
!
interface FastEthernet0/24
switchport access vlan 40
no ip address
!
