Today I updated my PC that runs stable NixOS 23.11 and that hasn’t been updated for approx ~3 weeks. After rebooting, I realized that the network was down. After some investigation I realized that USB NIC adapter ax88179_178a has a different MAC address and therefore static IP is not set (I set static IP to specific interfaces using systemd-network).
I thought that is strange and I updated my second PC which also had outdated NixOS and also has the same model of USB adapter and again, the MAC changed after reboot.
I didn’t change my configuration so I assume something changed in NixOS default configuration and I’m now getting random MACs on each reboot. Or maybe kernel is built with different options.
I don’t know how to fix it… My only hope was that Network Manager is doing something funny but I checked and those interfaces are unmanaged and I also tried and removed Network Manager and it didn’t help…
Thank you. For wired NICs I use systemd-network and after reading your post I completely removed Network Manager and it still doesn’t work (the mac address changes every reboot).
My assumption is that something changed in the last kernel update or in systemd-network but I can’t figure out what.
And all other laptops / PCs are OK - the only problem is those with ax88179_178a
And it’s weird that something changed since I’m on stable 23.11.
Not a suggestion: I think I need to replicate your situation because that may probably allow me to circumvent the undocumented lack of a setting in the Linux distro I have on my non-NixOS machine mainly because I can’t change it (see https://www.reddit.com/r/AllExceptNeeded/s/vONJktmxky)