一台主机用浏览器无法访问到域名为www.pku.edu.cn，并且在这台主机上执行ping命令时有如下信息 C:\>ping www.pku.edu.cnping www.pku.edu.cn[162.105.131.113] with 32 bytes of data:Request timed out.Request timed out.Request timed out.Request timed out.Ping statistics for 162.105.131.113Packets:Sent=4,Received=0,Lost=4（100% loss）分析以上信息，可以排除的故障原因是( )