CentOS系统yum源使用报错：Error: Cannot retrieve repository metadata (repomd.xml) for repository: rpmforge.

服务器上的yum突然不好使用，使用yum的时候报错如下：
[root@bastion-IDC src]# yum list
......
Could not retrieve mirrorlist http://mirrorlist.repoforge.org/el6/mirrors-rpmforge error was
14: PYCURL ERROR 7 - "couldn‘t connect to host"
http://apt.sw.be/redhat/el6/en/x86_64/rpmforge/repodata/repomd.xml: [Errno 14]
PYCURL ERROR 7 - "couldn‘t connect to host"
Trying other mirror.
Error: Cannot retrieve repository metadata (repomd.xml) for repository: rpmforge.
Please verify its path and try again

解决办法：
下载新的CentOS-Base.repo 到/etc/yum.repos.d/
[root@bastion-IDC src]# cd /etc/yum.repos.d/
[root@bastion-IDC yum.repos.d]#

1）centos5.*的下载连接：
[root@bastion-IDC yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-5.repo

2）centos6.*的下载连接：
[root@bastion-IDC yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-6.repo

3）centos7.*的下载连接：
[root@bastion-IDC yum.repos.d]# wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo

然后执行以下命令：
[root@bastion-IDC yum.repos.d]# rpm -e rpmforge-release --nodeps
[root@bastion-IDC yum.repos.d]# yum clean all
[root@bastion-IDC yum.repos.d]# yum update

最后再次使用yum就ok了
[root@bastion-IDC yum.repos.d]# yum list