通过修改CentOS-Base.repo文件中的源地址来处理

vi /etc/yum.repos.d/CentOS-Base.repo

将原mirrorlist行注释掉，并在原baseurl下分别添加新的源地址。
新的源地址为http://vault.centos.org，我的操作系统是5.11可以找对应的源。

最终更改CentOS-Base.repo文件内容如下，加粗部分为新加的内容，斜体部分为注释掉的内容。

[base]
name=CentOS-5.11 - Base - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/5.11/os/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-5
#released updates
[updates]
name=CentOS-5.11 - Updates - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/5.11/updates/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-5
#additional packages that may be useful
[extras]
name=CentOS-5.11 - Extras - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/5.11/extras/$basearch/
gpgcheck=1
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-5
#additional packages that extend functionality of existing packages
[centosplus]
name=CentOS-5.11 - Plus - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/5.11/centosplus/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-5
#contrib - packages by Centos Users
[contrib]
name=CentOS-5.11 - Contrib - mirrors.aliyun.com
failovermethod=priority
baseurl=http://mirrors.aliyun.com/centos-vault/5.11/contrib/$basearch/
gpgcheck=1
enabled=0
gpgkey=http://mirrors.aliyun.com/centos-vault/RPM-GPG-KEY-CentOS-5
 

文件修改完毕后，执行清空yum源缓存。完成后即可正常使用yum命令了。

yum clean all