故障现象：

双方都是ADSL线路，一个在北京，一个在上海，从上海Ping北京IP 222.128.XX.191返回如下结果：

C:\>ping 222.128.XX.191

Pinging 222.128.XX.191 with 32 bytes of data:

Reply from 61.148.68.233: TTL expired in transit.
Reply from 61.148.68.233: TTL expired in transit.
...