Wifi Usb stopped working (Arch Linux)

Greetings Gemini AI: A member in the Linux Forum posted this message, and I don't have a clue what to tell him..?

Wifi Usb stopped working (Arch Linux)

I think this happened after an update but my Wifi Usb stopped working.

I used Network Manager to connect using my phone, and have internet now. (using systemd-networkd now).

I used Network Manager to connect the Wifi Usb, and although it says "connected", the internet isn't working.

I cannot ping google.ca or 8.8.8.8.

I also did this same test in a Qemu image using usb forwarding, and was able to scan and connect to the network.

But I didn't check if it gave internet. (it was from lan)

I'm using Arch Linux.

lsusb

Bus 001 Device 002: ID 148f:7601 Ralink Technology, Corp. MT7601U Wireless Adapter

That is a classic Arch Linux puzzle. The user's hardware is clearly working (since it connects and works in QEMU), but they have a routing or DNS conflict on the main system.

The "smoking gun" in their message is this: "I used Network Manager... (using systemd-networkd now)."

Running two network managers simultaneously is a recipe for disaster in Linux. They fight over the interface, routing tables, and /etc/resolv.conf, which explains why it says "connected" but can't even ping a raw IP like 8.8.8.8.

Here is a plan you can share with them to get their MT7601U adapter back online.
1. Resolve the "Software War"

The user mentioned using both NetworkManager and systemd-networkd. They need to pick one and disable the other. Since they are using a USB Wifi adapter, NetworkManager is usually the better choice for ease of use.

Run these commands to stop the conflict:
Bash

sudo systemctl stop systemd-networkd systemd-resolved
sudo systemctl disable systemd-networkd systemd-resolved
sudo systemctl restart NetworkManager

2. Check for Driver Conflicts

The MT7601U chipset sometimes struggles if the kernel tries to use the wrong module or if there's a power management issue.

Verify the module is loaded: Run lsmod | grep mt7601u.

Check for Errors: Run journalctl -k | grep mt7601u to see if the firmware crashed during the update.

3. Fix the Routing & DNS

If they can't ping 8.8.8.8, their Default Gateway is likely pointing to the wrong interface (possibly the phone tethering they used earlier).

Tell them to run these diagnostic commands:

ip route ? Look for the default via ... line. It should point to the IP of their router via the USB device (e.g., wlan0).

ip addr. Ensure the USB adapter actually has a local IP address (e.g., 192.168.1.x).

4. The "Clean Slate" Method

If the above fails, then try resetting the interface entirely:
bash

sudo nmcli networking off
sudo nmcli networking on

And if they are using a desktop environment like KDE or GNOME, suggest they delete the existing Wi-Fi connection profile in the settings and re-add it. Updates occasionally corrupt the saved credentials or security settings (WPA2/WPA3 transitions).
Summary for the Forum Member:

"It looks like you have a conflict between NetworkManager and systemd-networkd. Disable systemd-networkd, restart NetworkManager, and check your routing table with ip route. If you can't ping 8.8.8.8, your traffic is likely trying to exit through a non-existent gateway from your previous phone tether."

Thanks.. I'll tell him your keen solution... Closing for now...

You're very welcome! Hopefully, that clears up the "ghost" connection for them. Arch is a great teacher, but it definitely has a habit of testing your patience when two services try to sit in the same chair.

Whenever you or your forum friends hit another snag, you know where to find me. Good luck to the user!