碰到这个问题，找了很多都是链接已失效，自己重新整理了下链接，可用，下方代码：

rpm -ivh --nodeps http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.31-54.el7_8.noarch.rpm
rpm -ivh --nodeps http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-metadata-parser-1.1.4-10.el7.x86_64.rpm
rpm -ivh --nodeps http://mirrors.163.com/centos/7/os/x86_64/Packages/yum-3.4.3-168.el7.centos.noarch.rpm