问yum报错请问怎么解决？

[root@VM_88_10_centos ~]# yum update                 
Loaded plugins: fastestmirror, langpacks
Repository epel is listed more than once in the configuration
Loading mirror speeds from cached hostfile
http://mirrors.tencentyun.com/epel/7/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.tencentyun.com; Unknown error"
Trying other mirror.
http://mirrors.tencentyun.com/centos/7/extras/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.tencentyun.com; Unknown error"
Trying other mirror.
http://mirrors.tencentyun.com/centos/7/os/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.tencentyun.com; Unknown error"
Trying other mirror.
http://mirrors.tencentyun.com/centos/7/updates/x86_64/repodata/repomd.xml: [Errno 14] curl#6 - "Could not resolve host: mirrors.tencentyun.com; Unknown error"
Trying other mirror.
No packages marked for update