Linux 安装mtr

1.yum install mtr -y

报错：No more mirrors to try.

 

 2.yum clean all

　yum makecache

　yum -y update

 

 3.重新安装 

　yum install mtr -y

 4.查看是否安装成功

　 yum list installed |grep mtr

 疑问：重新安装依然报错：No more mirrors to try，但是查看却有？