Fedora33 KVM host issues with bridged network for Debian guests

Hey community,

i found a strange behavior of network connections for KVM-guests on a Fedora33-Desktop host.
I set up a network bridge with nmcli and add my usb-c dock interface as a slave to it.
After that i installed a Debian-KVM-guest with virt-manager with the netinst-image.
The installation runs smoothly and no problems appear. Finaly with the running VM it looses the network-connection randomly for a minute or more to finally appear again for a few seconds.
On my Fedora host the network connection over the bridge runs smoothly without any issues.

STP is disabled, the guest has its own static ip and everything seems as it should work.

The funny thing is, that the logs of NetworkManager (journalctl -u NetworkManager) on my Fedora machine show, that the connection seems to re-initiate every minute or so, but nothing feels like it really does.
Anyone had the same or a similar issue?
I’m usually a Debian user/administrator, and only use Fedora, cause it runs on my Thinkpad without any issues.

I’ve been bit several times changing network settings related to virt-manager outside of virt-manager. I’d recommend trying to use a solution within virtual networks.

You also need to be connected to “QEMU/KVM” and not “QEMU/KVM User Session” to use virtual networks.

This advice may or may not be useful depending on your experience level, this is just my experience with it.

Hey Ulfnic,
i only had good expierence with managing networks outside of virt-tools like virsh or virt-manager, thats why i went this way.
Currently my Fedora is also displaying that there is no network-connectivity every minute or so, but it has no impact on my connections. Maybe there is something wrong there.
Kernel-Log also don’t take me anymore further, there is nothing usb, network, pcie related message, except something about wifi, which i’m not using.
As i’m more a Debian user and don’t have the time to debug my working device this long, i’ll change distros for now, since there is a better support for rx640 gpu.

Thanks for trying to help.