install di vps centos

para akang saya mau nanya, saya ingin menginstal software di vps centos saya, tapi tidak bisa, saya udah coba yum update tapi muncu error ini :
[root@server ~]# yum update
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=5 … mp;repo=os error was
[Errno 4] IOError: <urlopen error (-3, 'Temporary failure in name resolution')>
Error: Cannot find a valid baseurl for repo: base

kenapa yah,, ???