(http://www.krizna.com/centos/how-to-setup-network-in-centos-6/)
It was mentioned that CentOS 6, not like previous versions, will not have network after first installation.
First check the network devices: "ip a" (ipconfig will not show a device while this command will)
Then, edit the configuration file at /etc/sysconfig/network-scripts, and start network with "service network start"