Virtual Machine Manager Networking Broke After Update

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1

I have a desktop running Fedora that primarily uses a WiFi card to connect to the internet. There was an issue a month or two back with WPA supplicant authorization that I don’t fully understand which meant I purchased a WiFi extender with a Ethernet connection.

I updated the system over the weekend and checked everything was working except the virtual machine that I need for work. Typically, this is what broke.

I run Windows 11 virtual machine via Virtual Machine Manager. It uses the default NAT interface, with default settings. When booted the host machine is assigned an IP address on the default network and Windows shows a connected status.

On Fedora, the virb0 connection is active, with an ip address of 192.168.122.1, matching the default gateway on the host.

I’m usually pretty good at figuring things out and I’ve read most posts on here trouble shooting Virt Manager etc. I have some networking knowledge and a familiarity with Linux but no expertise. I’m not sure where to look next.

  • I have disabled the default firewall using systemctl stop firewalld.service.
  • I have tried to create a bridge between my WiFi connection and the virtual machine. Not successfully.
  • I have tried uninstalling Virtual Machine Manager and reinstalling it.
  • I have tried booting the virtual machine in Virtualbox which had the same issue.
  • I have booted the machine and watched the output of journalctl -f to see if there was any indication as to the issue.

I recently updated to the latest Fedora release.
Operating System: Fedora Linux 41
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Kernel Version: 6.11.7-300.fc41.x86_64 (64-bit)
Graphics Platform: Wayland

Little bit frustrated here and I’d appreciate any pointers in the right direction to remedy the issue.

3

I had the same issue after the upgrade to Fedora 41.

After searching around, I found out that in libvirt-1:10.4.0 the default firewall_backend changed from iptables to nftables.

So, I ended up editing /etc/libvirt/network.conf and using firewall_backend = "iptables". Then sudo systemctl restart libvirtd and the internet works in guest now.

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4

By default, Fedora switched from iptables to nftables quite some releases ago.

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5

That could be, but I didn’t have this issue with the default settings on Fedora 40. It just broke after the Fedora 41 upgrade.

If there’s a better way to fix the issue, please do let us know since I ended up with the aforementioned workaround by searching around.

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6

A big thank you to everyone who replied. The issue was indeed the update to libvirt-1:10.4.0and a change to the default firewall_backend

I followed the suggestions here and got more context at the links below to solve my problem.

The solution boiled down to editing

/etc/libvirt/network.conf

with
sudo nano etc/libvirt/network.conf

and editing

#firewall_backend = "nftables"

to

firewall_backend = “iptables”

I rebooted the system as I was unsure which service to restart to ensure the changes were active.

When trying to boot the virtual machine, I ran into an issue with the virbr0 connection and needed to delete it and run

sudo virsh net-start default

Really glad I was able to muddle through this with help. Thanks.

Context Reading
https://bbs.archlinux.org/viewtopic.php?id=296548