When you install a fresh RHEL(/CentOS/Scientific Linux…) 6 VM and then clone it including MAC address change, it won’t get IP from DHCP because there is a persistent udev rule and a network script bound to the old MAC.
You can remove/modify them manually at
/etc/sysconfig/network-scripts/ or you can use
virt-sysprep to do it for you:
virt-sysprep --enable net-hwaddr,udev-persistent-net -d virt-vm-name
This tool can do more stuff to clean/configure your VM, see:
You can run it on inactive virt domain (
-d) or a disk image (