l2tp无法接收包

eagleonhill

如图，ping网址203.208.33.100,确定route已经设置成通过ppp0的网关58.207.254.1  
用wireshark截eth0的包，抓到了ping reply，但ppp0中并无此项，ping命令中接收到的包数量为0
ifconfig for ppp0:
ppp0      Link encapoint-to-Point Protocol
          inet addr:58.207.176.128  P-t-P:58.207.254.1  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1400  Metric:1
          RX packets:11 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:426 (426.0 B)  TX bytes:386 (386.0 B)

该事件为RP事件，有时正常