The latest versions of the kernel now rely on the BIOS enumeration of device names which means that the name of the network interface can change depending on your bus configuration (specifically where your network interface is connected).
The new naming convention may appear very odd but it is logical once you understand how it works. Wired network interfaces will start with en and wireless interfaces will start with wl, but then it gets a bit strange. Depending on your system’s hardware configuration this can be followed by a p followed by a number indicating which PCI bus it is on; and/or an s followed by a number which indicates which slot the device is in; or an o followed by a number if it is an on-board device. There may also be an f followed by a number if there are multiple interfaces on the same card.
What can make it confusing is that just because your machine has two interfaces on the motherboard it does NOT mean that they are going to be on-board devices, as the device names will depend on how the motherboard is designed. In practice they may not even be on the same PCI bus!
If you don’t like your machines having device names that depend on the hardware you can continue to use the old network device names by passing a couple of parameters to the kernel when your system boots.
To do this you need and edit /etc/default/grub as a superuser using your favourite editor (or what ever you have installed – I’ve chosen vi as it is almost always available), and add net.ifnames=0 biosdevname=0 to the kernel parameters.
Generally I prefer to comment out the original line before making any changes, as I’ve done here.
Then you need to update grub. If you are using a Debian or a related distribution like Ubuntu then you need to use update-grub to do this.
Alternatively if you are using a RedHat or a related distribution like CentOS then you need to use grub2-mkconfig.
You will also need to update the network device names. If you are using a Debian based system you will need to edit /etc/network.interfaces.
If you are using RedHat or CentOS you will need to rename and edit the interface specific files in /etc/sysconfig/network-scripts.
Then you will need to reboot for these changes to take effect.