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Re: internal error: Network is already in use by interface virbr0

On 9/17/21 7:11 AM, Michael Ströder wrote:

I'm using libvirt 7.7.0 on openSUSE Tumbleweed.

Until recently everything just worked. But now my virtual NAT network is
not usable anymore.

Starting a VM I get this error:

# virsh start ae-dir-suse-p1
error: Failed to start domain 'ae-dir-suse-p1'
error: Requested operation is not valid: network 'vnet1' is not active

Manually starting the network does not work either:

# virsh net-start vnet1
error: Failed to start network vnet1
error: internal error: Network is already in use by interface virbr0

In syslog I find:

libvirtd: 6325: error : networkCheckRouteCollision:296 : internal error:
Network is already in use by interface virbr0

What does that mean? Where to look for a config error?

Someone else (probably libvirt itself, for libvirt's "default" network) has created a bridge device called virbr0, and has set it up on the same subnet that you are trying to use for your network, which is confusingly called "vnet1".

My first guess is would be that either:

1) you previously did not have the libvirt-daemon-config-network package (which adds the default network to the host and sets it to auto-start) and now it is installed, and being started before the "vnet1" network.


2) you *did* have libvirt-daemon-config-network (and thus the libvirt default network) installed, but for whatever reason your libvirtd was starting your "vnet1" network first, then failing to start the "default" network.

To fix this problem, change the subnet used by one or the other of the networks such that they don't conflict (e.g. if both have, change one of them to using "virsh net-edit $networkname", then virsh net-destroy and virsh net-start both networks.

Alternately, if you never use libvirt's default network, just net-destroy it and set it to not auto-start:

   virsh net-destroy default
   virsh net-autostart default --disable
   virsh net-start vnet1

Or, another alternate possibility - instead of using your own NAT network, just edit your guest config to use libvirt's default network and set net-autostart disable for your vnet1 network (if you have any extra config in that network, like static DHCP addresses, you'll want to move it into the default network, then net-destroy/net-start the default network so those changes take effect).

Once you've changed the config, it should persist through future reboots of your host.

When restarting libvirtd itself I see the following syslog warning message:

libvirtd: 5733: warning : netcfIfaceRegister:1287 : Failed to initialize
libnetcontrol.  Management of interface devices is disabled

That's unrelated and unimportant. Most probably the libvirt APIs affected by that have *never* operated properly on openSUSE (it uses a "netcf-lookalike" that, AFAIU, accepts the same XML as netcf and has some of the same functions, but was never really "complete", and is probably just as much abandonware as netcf (which was abandoned, by me, last year)), and it's likely that you never had the libnetcontrol package installed at all, and have always had this warning but just didn't notice it until now.

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