vi /etc/udev/rules.d/70-persistent-net.rules
when you clone a vm, it will assign the nic a new mac.
if you didn’t clear these rules prior to cloning the disk, the mac will be assigned to the next available ethernet interface ie: eth1
delete the eth0 line, rename the eth1 to eth0, reboot.
Alteratively just delete the file. For template clone images just delete the file as the last thing you do and it will create a new on boot (when its cloned and has new mac addresses).