拓扑如下：
DHCP server（vlan 101）-------G0/0/1-S5700-G0/0/2-------client1（vlan101）
|
G0/0/3
Client2（vlan 110）
主要配置如下：
#
interface Vlanif101
ip address 192.168.1.1 255.255.255.0
dhcp select global
#
interface MEth0/0/1
#
interface GigabitEthernet0/0/1
port link-type trunk
port trunk allow-pass vlan 101
#
interface GigabitEthernet0/0/2
port default vlan 101
#
interface GigabitEthernet0/0/3
qinq vlan-translation enable
port link-type trunk
port trunk allow-pass vlan 110 101
port vlan-mapping vlan 110 map-vlan 101