Windows 10 - Can ping anything but hostnames

Question

My computer is currently connected via LAN to a powerline adapter, the other end to an access router. When trying to ping the router with its hostname (fritz.box), it says non-existent domain. Using IP addresses works just fine.

Trying this on another computer with win10 and the same ethernet cable works as expected. There's also another device connected to the powerline via LAN, somehow I can ping it using its hostname. But only when its connected to LAN and only over IPv4. Turning off IPv6 doesn't help.

This problem is only in my local network, pinging google.com works fine.

What I've tried so far:

• Disabled IPv6
• Disabled Firewall and Anti Virus
• restarted everything
• Windows Troubleshooter...
• using WiFi (connected to powerline)

Here the output from ipconfig, IPv6 still deactivated:

Ethernet-Adapter Ethernet:

   Connection-specific DNS-Suffix. . : fritz.box
   IPv4 Address. . . . . . . . . . . : 192.168.178.4
   Subnet Mask . . . . . . . . . . . : 255.255.255.0
   Default Gateway . . . . . . . . . : 192.168.178.1

For any additional infos, just ask

I am aware of this question "Windows 10 - Can ping IP but cannot ping hostname on my LAN" but the only answer there doesn't do anything for me.

Answer 1

What DNS servers are you using? Is it the Fritzbox that is working as DNS?

You can find out typing ipconfig /all

Answer 2

As stupid as it sounds, it turns out that Cloudflare WARP still was running in the background. There was no indication other than some network activity in the task manager after I sorted by network load. Not even in the system tray.