Network adapter gone? Check the bus before the connection.

1. Establish which layer failed

A network outage can happen while the PCI device is healthy. This guide is for an adapter that reports 7f or becomes inaccessible, not every weak Wi-Fi signal or failed DHCP lease. USB Wi-Fi adapters use a different enumeration path and should not be diagnosed solely with lspci.

lspci -Dnnk
ip -brief link
# Replace this example with your network controller address.
sudo lspci -s 0000:02:00.0 -vv
sudo journalctl -k -b --no-pager

Record the PCI IDs, loaded driver and whether a network interface exists. If PCI access is healthy but the interface cannot connect, move to that driver’s firmware, radio, link or network configuration checks. If access is lost, DNS changes cannot restore the controller.

2. If it happens after Windows, test a complete shutdown

The Linux Wireless iwlwifi documentation identifies Windows Fast Startup as a possible cause of Wi-Fi initialization problems on dual-boot systems. It recommends disabling that Windows shutdown feature and testing again. This guidance concerns initialization; it does not prove every 7f failure has this cause. Linux Wireless: iwlwifi and Windows Fast Startup.

1. Save your work in Windows.
2. Open Control Panel → Power Options → Choose what the power buttons do. If needed, select the option to change currently unavailable settings.
3. If “Turn on fast startup” is offered, turn it off, save the setting and shut down normally.
4. Boot Linux and compare the adapter state. Record whether the original trigger still reproduces.

Windows Fast Startup and a firmware menu item called Fast Boot are different settings. Menu details vary by Windows version and policy. For non-Intel adapters, use this as a controlled initialization comparison and check your adapter vendor’s guidance rather than assuming Intel-specific behavior applies.

3. If it happens after sleep, compare the transition

Keep a working snapshot, reproduce one suspend/resume cycle if doing so is safe for your work, and capture the failed state. Record whether AC versus battery changes the result. If a device sysfs directory still exists, these reads can add context:

# Replace the address; not every file exists on every kernel.
cat /sys/bus/pci/devices/0000:02:00.0/power/runtime_status
cat /sys/bus/pci/devices/0000:02:00.0/power/control

Runtime status and policy are context, not proof of a fault: a suspended idle device can be normal. The kernel’s runtime-PM documentation explains the policy interface. Avoid turning off power management across the machine as the first experiment. Linux kernel: runtime power management.

4. For embedded Ethernet, include the hardware path

A NVIDIA Jetson TX2 support thread documents this exact error on an Ethernet controller on a custom carrier. The support discussion directs investigation toward a lost PCIe link, including reset and reference-clock behavior. It is a specific incident, not a confirmed fix for every Ethernet card. NVIDIA forum: Ethernet controller on a Jetson TX2 custom carrier (2018).

For a custom board, include the carrier revision, endpoint, upstream switch, power rails, clock/reset design and time to failure. For a laptop or desktop, include the exact adapter, motherboard and BIOS instead. Select a supported driver/kernel/firmware comparison based on that evidence.

Arrange local access before any action that could disconnect the management NIC. Use an orderly restart or the manufacturer’s power-off procedure for recovery, then retest the original trigger.

Common network questions

Should I reset NetworkManager?

Not as a remedy for an inaccessible PCI device. Check the device layer first; restarting networking is more relevant when the adapter remains present and operational.

Should I install an out-of-tree Realtek driver?

First identify the exact PCI ID and in-use driver, then consult your distribution’s supported packages. A module change needs evidence and a rollback route; the error string alone is not enough.

When is the issue fixed?

When the adapter remains accessible and passes actual traffic after the previously failing shutdown, resume or operating interval—not merely when the interface name reappears.