Network interface naming rules changed with Debian 9. There are a few reasons behind this, you can read the details here:
If you just upgraded your system from Debian-8 to Debian-9, old ethXX schema will continue to work. But, if you install a fresh Debian-9 system, new schema will be used.
So, old schema is deprecated in Debian 9, and will not be supported any more in Debian 10 (similarly Ubuntu 18.04 LTS).
Now you can switch the old schema with adding new kernel parameters:
/etc/default/grub file and add
net.ifnames=0 biosdevname=0 parameters to GRUB_CMDLINE_LINUX variable like that:
- Update the grub config and reboot the system:
$ sudo update-grub
$ sudo reboot