[CentOS] Could not retrieve mirror list while using yum command

Hi

I wanted to download and install the net-snmp package. Usually on my 
other CentOS boxes i use the following command to do it:

yum install net-snmp

I was able to successfully install net-snmp on 4 of my CentOS boxes but 
not on one of them. It reports me the following error message:

[root at localhost yum.repos.d]# yum install net-snmp
Loaded plugins: fastestmirror
Determining fastest mirrors
Could not retrieve mirrorlist 
http://mirrorlist.centos.org/?release=5&arch=i386&repo=os error was
[Errno 4] IOError: <urlopen error (110, 'Connection timed out')>
Error: Cannot find a valid baseurl for repo: base


Other output that can be some use is :

[root at localhost yum.repos.d]# ls
CentOS-Base.repo  CentOS-Media.repo


Can someone please let me know what the issue is ? and how to get it 
working ?

Thanks
Jatin