Clone Debian auf einer Vmware ESX Plattform

This is caused by udev being used to make sure that the same eth0/eth1, etc., name is always given to an interface on reboots once it has been assigned. When an interface with a recognized MAC address is found during boot, it is assigned the previously assigned port name. A by-product of this logic is that if an interface is found with an unrecognized MAC address, then it is assigned a new port name.
The 'recognized' MAC addresses are stored in the file "/etc/udev/rules.d/z25_persistent-net.rules". If you delete this file and then reboot, your network interfaces will be named starting at 'eth0' (and the file will be recreated).
You can, of course, delete the file in the 'master' VM that you will be cloning, and then when you create a new copy, the network interface will be named 'eth0' when it first boots. Just be sure you never boot the master, or the file will be recreated in it, locking 'eth0' once again to the MAC address of the master VM.