本帖最后由 YilinChen 于 2018-3-26 12:10 编辑
亲，800系列路由器，只有 Fa4 是三层口，其它Fa0 - Fa3是二层交换口（集成一个小交换机），所以你应该在Fa4三层口上配置，参考配置如下：
interface Dialer10
ip address negotiated
no ip proxy-arp
ip mtu 1492
ip nat outside
encapsulation ppp
ip tcp adjust-mss 1452
dialer pool 10
dialer-group 10
ppp authentication pap callin
ppp pap sent-username ABCDEF password 7 ABCDEF
interface FastEthernet4
pppoe enable
pppoe-client dial-pool-number 10
interface Vlan1
ip address 172.16.1.1 255.255.255.0
ip nat inside
ip access-list extended PAT
permit ip 172.16.1.0 0.0.0.255 any
ip nat inside source list PAT interface Dialer10 overload
ip route 0.0.0.0 0.0.0.0 Dialer10