My Proxmox node rebooted, and suddenly the host was unreachable via SSH. I had to plug in a physical monitor and keyboard only to find that my primary network interface, which had been enp4s0 for months, had decided to rename itself to enp5s0 . Because my /etc/network/interfaces file was explicitly tied to enp4s0 , the bridge didn't come up, the IP wasn't assigned, and I was locked out of my own hardware. What I expected I expected the Linux kernel to consistently enumerate my PCIe devices. In a static hardware environment where nothing has moved, the PCI bus address should be deterministic. If the NIC is plugged into the same slot and the BIOS hasn't changed, enp4s0 should stay enp4s0 forever. This is the "happy path" most documentation assumes. What actually happened The reality is that PCIe enumeration is not always a constant. I'm using a mix of onboard NICs and a PCIe expansion card. I also have a GPU passed through to a VM.…