我已经设置了一个 PPPoE 服务器和客户端。我无法 ping 连接在 ISP 路由器上的任何 IP 地址。我仍在弄清楚为什么这不起作用。但目前最简单的问题是：无法ping通本地连接的Dialer1接口。怎么了？

hostname R1

interface GigabitEthernet0/0/0
 description R1 --> MLS1
 ip address 10.1.0.5 255.255.255.252
 negotiation auto

interface GigabitEthernet0/0/1
 description R1 --> ISP1
 no ip address
 speed 1000
 no negotiation auto
 pppoe enable
 pppoe-client dial-pool-number 1

interface GigabitEthernet0/0/2
 no ip address
 shutdown
 negotiation auto

interface Dialer1
 ip address negotiated
 encapsulation ppp
 dialer pool 1

ip route 0.0.0.0 0.0.0.0 Dialer1

Dialer1 接口确实通过 PPPoE 获得 IP 地址：

R1#sh ip int brief
Interface              IP-Address      OK? Method Status                Protocol
GigabitEthernet0/0/0   10.1.0.5        YES NVRAM  up                    up      
GigabitEthernet0/0/1   unassigned      YES manual up                    up      
GigabitEthernet0/0/2   unassigned      YES NVRAM  administratively down down    
GigabitEthernet0       unassigned      YES NVRAM  administratively down down    
Dialer1                172.16.0.2      YES IPCP   up                    up      
Virtual-Access1        unassigned      YES unset  up                    up      
Virtual-Access2        unassigned      YES manual up                    up