阿里云的下载已经失效，请前往官网下载地址下载。
</br>
https://wiki.centos.org/Download
</br>
http://vault.centos.org/6.8/isos/x86_64/
</br>
直接下载这个也可以
</br>
64bit
</br>
http://archive.kernel.org/centos-vault/6.8/isos/x86_64/CentOS-6.8-x86_64-bin-DVD1.iso

</br>
32bit
</br>
http://archive.kernel.org/centos-vault/6.8/isos/i386/CentOS-6.8-i386-bin-DVD1.iso