Ubuntu – In Ubuntu 16+, for a network interface “ens192”, where does the “192” come from

interfacenetworking

We have dozens of virtual machines in several data centers around the world. When upgrading an Ubuntu VM from 14 to 16 (as a step toward upgrading them to Ubuntu 18), the network interface names change. I am aware of this, and I know why they change, so that is not my question. My question is where does the number (the 33 in ens33, the 192 in ens192, etc.) come from? I have read many StackExchange questions and answers about what to do to get the server working: that is not the problem. What I want to know is how to predict what the ens### will be before the server is upgraded to Ubuntu 16. I have looked at lshw and lspci, and I can't see any reason why these numbers are chosen.

Please: where does the 192 (or 33, or anything else) come from?

Best Answer

While I don't know why they are the ensXX format, if you want to disable them to have consistent naming across servers and get the legacy ethX, you'll want to set the net.ifnames=0 biosdevname=0 kernel boot arguments in GRUB or your bootloader in general.