ping 应该是ping hostname/ip 吧，应该没有ping url 的吧？那么 ping http://www.baidu.com 是个啥意思？还能通。

 localhost:~ zhoumengkang$ ping http://wwww.baidu.com
PING http://wwww.baidu.com (202.106.199.34): 56 data bytes
64 bytes from 202.106.199.34: icmp_seq=0 ttl=249 time=88.625 ms
64 bytes from 202.106.199.34: icmp_seq=1 ttl=249 time=8.077 ms

 localhost:~ zhoumengkang$ ping www.baidu.com
PING www.a.shifen.com (61.135.169.125): 56 data bytes
64 bytes from 61.135.169.125: icmp_seq=0 ttl=56 time=21.843 ms
64 bytes from 61.135.169.125: icmp_seq=1 ttl=56 time=9.773 ms
64 bytes from 61.135.169.125: icmp_seq=2 ttl=56 time=50.860 ms
64 bytes from 61.135.169.125: icmp_seq=3 ttl=56 time=13.209 ms
64 bytes from 61.135.169.125: icmp_seq=4 ttl=56 time=7.853 ms