华为三层交换机
工作原理：一次交换，多次转发
作用：实现vlan间的数据互通
ensp拓扑图如下：
SW2
<Huawei>sys [Huawei]sysname SW2 [SW2]vlan batch 10 20 [SW2]int e0/0/2 [SW2-Ethernet0/0/2]port link-type access [SW2-Ethernet0/0/2]port default vlan 10 [SW2-Ethernet0/0/2]un sh [SW2-Ethernet0/0/2]int e0/0/3 [SW2-Ethernet0/0/3]port link-type access [SW2-Ethernet0/0/3]port default vlan 20 [SW2-Ethernet0/0/3]un sh [SW2-Ethernet0/0/3]int e0/0/1 [SW2-Ethernet0/0/1]port link-type trunk [SW2-Ethernet0/0/1]port trunk allow-pass vlan all [SW2-Ethernet0/0/1]un sh [SW2-Ethernet0/0/1]int g0/0/1 [SW2-GigabitEthernet0/0/1]port link-type trunk [SW2-GigabitEthernet0/0/1]port trunk allow-pass vlan all [SW2-GigabitEthernet0/0/1]un sh
