The original network device naming convention in Linux, pre 2009, was to name each interface ethX as the device was discovered during boot. This caused problems on machines with mulitple interfaces when interfaces were changed. After 2009, Linux swiched to the Consistent Network Device Naming convention which follows a set of naming conventions based on firemare indexes and PCI slot numbers.

In Proxmox, I still had issues with Minisforum NAB5 and NAB6 where network interfaces would randomly reorder on reboot. To fix this, I renamed the devices by creating systemd link files.

For each nic I created a systemd.link network device configuratoin. This matches the udev property ID PATH and renames the nic to etherX.

First you have to find the ID PATH of your network devices using the udevadm command. The example below shows the output for a system with a built-in nic0 and USB nic1.

$ udevadm info -q property --property=INTERFACE --property=ID_PATH --subsystem-match=net -p /sys/class/net/*
Unknown device "/sys/class/net/bonding_masters": No such device
INTERFACE=lo
INTERFACE=nic0
ID_PATH=pci-0000:02:00.0
INTERFACE=nic1
ID_PATH=pci-0000:00:10.0-usb-0:1:1.0

Then create the overrides and reboot.

/etc/systemd/network/10-ether1.link

[Match]
Path=pci-0000:02:00.0
[Link]
Name=ether1

/etc/systemd/network/10-ether2.link

[Match]
Path=pci-0000:00:10.0-usb-0:1:1.0
[Link]
Name=ether2