DHCP on newly installed system?

Did somebody change the install in some way that would cause a newly 
installed system to do DHCP by default, without going through the proper 
steps of creating an /etc/sysconfig/network-scripts/ifcfg-ethX file?

maso's main machine could not access the internet, so he said his 
marvell yukon interface was not working properly.  Upon further 
investigation, the interface was up and had an IP address, but it had no 
default route or resolv.conf or ifcfg-ethX file.   Any idea how that 
might happen?