条件：

R1为DHCP配置网关，S1为二层交换机

要求：

PC1获取到vlan10地址，PC2获取vlan10地址，PC3获取vlan20地址

方法1：

S1正常配置vlan10，20，配置与R1相连的1口为trunk口

R1的1口，配置单臂路由，终结vlan10、20

AR1的配置：

dhcp enable
#
ip pool 1
 gateway-list 10.10.10.1 
 network 10.10.10.0 mask 255.255.255.0 
 excluded-ip-address 10.10.10.2
#
ip pool 2
 gateway-list 10.20.20.1 
 network 10.20.20.0 mask 255.255.255.0 
#
interface GigabitEthernet 0/0/1.1
 dot1q termination vid 2   
 ip address 10.10.10.1 24
 arp broadcast enable   
#
interface GigabitEthernet 0/0/1.2
 dot1q termination vid 3   
 ip address 10.20.20.1 24
 arp broadcast enable    
#

方法2：

将R1的1口配置为二层的trunk口，配置vlan10、20的vlanif网关为dhcp网关

interface GigabitEthernet0/0/1
 portswitch
 port link-type trunk
port trunk allow-pass vlan 10 20
#
int vlanif 10
 ip addr 10.10.10.1 24
 dhcp select interface
#int vlanif 20
 ip addr 10.20.20.1 24
 dhcp select interface