1.配置虚拟端口：
interface Dialer1
ip address negotiated
ip nat outside
ip virtual-reassembly in
encapsulation ppp
ip tcp adjust-mss 1452
dialer pool 1
dialer-group 1
ppp authentication pap callin
ppp pap sent-username USER_NAME password 0 PASSWORD
2.vpdn虚拟拨号连接
vpdn enable 开启虚拟拨号
vpdn-group pptp 定义组名
Default PPTP VPDN group
accept-dialin 请求拨号
protocol pptp 拨号协议
virtual-template 1
3.外网接口：
pppoe enable group global
pppoe-client dial-pool-number 1
4.配置默认路由