Re: virt-manager and qemu: virtual networking missing
On Sat, 25 Oct 2025 13:17:00 -0600
Charles Curley <charlescurley@charlescurley.com> wrote:
> What am I missing?
From what folks have said here and elsewhere, apparently using a
virtual network with wifi is problematic. I began to wonder if that was
my problem. So I ran "install virt-manager" on a desktop with Ethernet
only. That produced a default network. Starting that network produced
the virtual interface virbr0 that the default network wanted.
The libvirt documentation on virtual networking is silent on the use of
wifi interfaces. https://wiki.libvirt.org/VirtualNetworking.html The
wiki does mention the issue for bridged networks, not for NATted
networks (the default network is NATted).
https://wiki.libvirt.org/Networking.html#host-configuration-bridged
Given the ubiquity of laptops and wifi, I wonder about the wisdom of
such a restriction.
As near as I can tell the problem with using wifi isn't wifi per se.
Apparently some wifi routers track MAC addresses. Your computer gets on
the network using its MAC address. Your virtual machines have
different MAC addresses. Linux's virtual networking is transparent,
meaning it does not play with the virtual machines' MAC addresses. So
the wifi router sees this new MAC address from the VM, and rejects it.
Apparently my wifi access points do not care about this, as I have run
VMs on laptops on my home network for years without issue. And there are
solutions out there based on ebtables.
I am considering filing a bug. I believe the libvirt folks should solve
this problem, not Debian packagers.
--
Does anybody read signatures any more?
https://charlescurley.com
https://charlescurley.com/blog/
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