Take a look at your ifcfg-ethX configuration file under /etc/sysconfig/network-scripts directory (substitute ethX with your network interface, e.g. eth0). In my case, "Minimal" install of CentOS 6 configured the ethernet interface not to start automatically (line ONBOOT="no") and to rely on NetworkManager (NM_Controlled="yes"). This is odd, as NetworkManager is not installed by default. Thus, even though the system is in runlevel 3 and you should have networking (if...
