Ethernet interface IDs change and break network

post by gauss256 on Jun 11, 2021

Lambda Blade, Ubuntu 18.04 and Ubuntu 20.04

The ID of our primary ethernet interface frequently changes after a software update, adding a GPU, etc. The result is that DHCP is not used and there is no network connectivity. Running sudo dhclient -r; sudo dhclient fixes it until the next reboot but that is just a temporary fix.

How can we configure things so that the interfaces always use DHCP at startup? Currently, the file /etc/netplan/01-netcfg.yaml looks like this:

network:
  version: 2
  renderer: networkd
  ethernets:
    eno0:
      dhcp4: true
    enp96s0f0:
      dhcp4: true
    enp97s0f0:
      dhcp4: true

We are only using one interface, but every time a new interface ID shows up, we add it to this file to try to catch it next time. This is obviously just a hack and is not robust. What is the right way to do this?

post by jeremy on Jun 15, 2021

This name change is because of the way SystemD enumerates devices - I’m not sure why this would be the intended behavior.

Put the following in /etc/udevd/rules.d/10-ethernet.rules:

SUBSYSTEM=="net", ACTION=="add", ATTR{address}=="01:23:45:67:89:ab", NAME="eth1"

The address above will be the MAC of the NIC, and eth1 will be the name you want to give it.

Hope that helps! 🙂