p128p1 and UDEV 70-persistent-net.rules

When your system boots up, the kernel identifies sets up physical names for the network interface cards and UDEV maps those to logical names, such as eth0. This is usually pretty stable because UDEV records how it mapped an interface when it first saw it, so it can map it the same afterwards. However, if your eth0 interface disappears and is replaced with one named p128p1 then UDEV is having a problem with the file it records those mappings in.

Those mappings are (in ubuntu) in /etc/udev/rules.d/70-persistent-net.rules

Options:

Regenerate the file. On some systems you can remove the file, reboot and it will be regenerated. However, there are occasional bugs with UDEV that prevent that and nothing happens

Repair the file. You can put a line like this in the file to map the name

sudo vim /etc/udev/rules.d/70-persistent-net.rules
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="b8:ac:6f:65:31:e5", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
Also, review the interface file to make sure it matches

sudo vim /etc/network/interfaces

# The primary network interface
auto eth0
iface eth0 inet dhcp
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