I stumbled across this issue a long time ago and it is still present today. Adding or removing NIC’s from a Linux box, or even replacing them renumbers or messes with the numbering for each NIC. For example if you have 1 NIC and add a second, sometimes it won’t show up as eth0 and eth1, it will show up as eth0 and rename1. Or even sometimes, your original eth0 will be renamed to rename1 and the new NIC will be named eth0 when added. Yikes! Talk about confusion.
It appears that this naming information is stored in a file located in /etc/udev/rules.d/70-persistent-net.rules
So if you want to reset the numbering completely, delete this file and reboot! Now you have clean eth# numbering again!
NOTE: You can also manipulate and edit this file rather than deleting it.