vlan隔离：把广播和故障，可以隔离。同时，正常的通信也被隔离了。
vlan互连：用三层交换机作网关，把不同vlan之间的正常通信连通。

<Huawei>sy    
<Huawei>system-view 
Enter system view, return user view with Ctrl+Z.
[Huawei]vlan 10

[Huawei-vlan10]vlan 20
[Huawei-vlan20]q

[Huawei]undo in en
Info: Information center is disabled.

[Huawei]int g0/0/1
[Huawei-GigabitEthernet0/0/1]port li    
[Huawei-GigabitEthernet0/0/1]port link-typ    
[Huawei-GigabitEthernet0/0/1]port link-type ac    
[Huawei-GigabitEthernet0/0/1]port link-type access
[Huawei-GigabitEthernet0/0/1]port default vlan 10

[Huawei-GigabitEthernet0/0/1]int g0/0/2
[Huawei-GigabitEthernet0/0/2]port li    
[Huawei-GigabitEthernet0/0/2]port link-t    
[Huawei-GigabitEthernet0/0/2]port link-type ac    
[Huawei-GigabitEthernet0/0/2]port link-type access 
[Huawei-GigabitEthernet0/0/2]port default vlan 20
[Huawei-GigabitEthernet0/0/2]q

[Huawei]sy    
[Huawei]int g0/0/3
[Huawei-GigabitEthernet0/0/3]port link-type trunk
[Huawei-GigabitEthernet0/0/3]port trunk allow-pass vlan 10 20
[Huawei-GigabitEthernet0/0/3]q

[Huawei]vlan 10
[Huawei-vlan10]vlan 20
[Huawei-vlan20]int vlan 10 
[Huawei-Vlanif10]ip add 192.168.10.1 255.255.255.0
[Huawei-Vlanif10]int vlan 20
[Huawei-Vlanif20]ip add 192.168.20.1 255.255.255.0
[Huawei-Vlanif20]

第一步：把两个交换机互连的接口配置为trunk
第二步：在三层交换机创建vlan
第三步：给vlan接口配上ip，作为pc的网关