Thanks Markus for the hint.
I’ve tested it and I have only a virbr0 and promisc is not shown for it.
So I have to try to force it? There are no entries for it at the libvirt manager.
I’ve two VM’s with a bridge to different networkinterfaces, shouldn’t be there two bridges also, virtbr0 and virtbr1? I’ve only one.
Yes, enable it and see if it helps:
ifconfig virbr0 promisc
To disable you may execute ifconfig virbr0 -promisc.
https://www.polarsys.ca/docs/linuxdocs/promiscuous.html
No, all your VMs are bridged to virbr0 to be in the same network, that should be ok.
Thanks again,
set the bridge to promisc, it is shown at ifconfig, but does not work. So I tried to restart the interface with
ifdown virbr0 && ifup virbr0
the message is
interface virbr0 is not configured
Ignoring unknown interface virbr0=virbr0.
Sorry, maybe you have to restart libvirt. I try to reproduce it in the evening.
Some docs:
Thanks Markus,
it’s no problem to restart the server at the next week. I write what has happened after restart at the next week.
Hello friends,
I restarted the server, but after restart the promisc entry at virbr0 is away again. So it doesn’t work for me.
I can do nmap to the nethserver ip, but not to the samba ip.
Just to avoid misunderstandings:
The bridge has to exist on the Ubuntu host and be set to promisc mode.
The VM has to use a network that’s mapped to the mentioned host bridge.
Which Ubuntu version is used?
yes the bridge exists on the ubuntu and was set to promisc mode, but after reboot it wasn’t set anymore.
I can’t map to the bridge, at the libvirt manager I only can choose bridge to a real networkadapter
14.04 with lubuntu desktop
Maybe it’s enough to enable promisc mode on eth2?
No, it’s not allowed, but thanks for your help again.
PS: I wanted to went to proxmox a long time ago, it’s an argument to do it faster 
You may create a bridge on the Ubuntu host, I tried it on Ubuntu 18.04:
If you don’t have ifconfig execute sudo apt-get install net-tools
Install bridge:
sudo apt-get install bridge-utils
Edit /etc/network/interfaces to add the new bridge (this example is for dhcp, static config is described here, scroll down to “Creating a persistent bridge”):
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
auto br0
iface br0 inet dhcp
bridge_ports ens33
bridge_stp off
bridge_fd 0
bridge_maxwait 0
Restart networking:
sudo /etc/init.d/networking restart
Enable promisc mode:
sudo ifconfig br0 promisc
Select the new bridge for the VM:
