How to set up a bridge for KVM in Ubuntu LTS 18.04?

Question

Virtualization

Good time of the day!
It is not possible to configure a bridge for KVM, the created bridge1 assigns the IP of the network card, and on the enp031f6 device the address disappears and only ipv6 remains. I tried to set statics, after a reboot I lost access to the network, but on the contrary it worked on a virtual machine.
GNU nano 2.9.3 /etc/network/interfaces
# ifupdown has been replaced by netplan(5) on this system. See
# /etc/netplan for current configuration.
# To re-enable ifupdown on this system, you can run:
# sudo apt install ifupdown
auto bridge1
iface bridge1 inet dhcp
bridge_ports enp0s31f6
bridge_stp off
bridge_fd 0.0
If you add the enp031f6 adapter settings here, then access to the network is lost. At the top right in the GUI, there is a question mark and an inscription, the connection is not controlled by anything.
ifconfig
bridge1: flags=4163 mtu 1500
inet 192.168.2.9 netmask 255.255.255.0 broadcast 192.168.2.255
inet6 fe80::da9e:f3ff:fe2c:ae73 prefixlen 64 scopeid 0x20
ether d8:9e:f3:2c:ae:73 10queuelen ( TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 enp0s31f6 : flags=4163 mtu 1500
inet6 fe80: :da9e:f3ff:fe2c:ae73 prefixlen 64 scopeid 0x20
ether d8:9e:f3:2c:ae:73 txqueuelen 1000 (Ethernet)
RX packets 1637 bytes 735264 (735.2 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1487 bytes 336879 (336.8 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 16 memory 0xdf000000-df020000
lo: flags=73 mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10
loop txqueuelen 1000 (Loopback)
RX packets 510 by1tes packets 340 (51.0 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 340 bytes 51041 (51.0 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vnet0: flags=4163 mtu 1500
inet6 fe80::fc54:ff:fe3e:29c prefixlen 64 scopeid 0x20
ether fe:54:00:3e:02:9c txqueuelen 1000 (Ethernet)
RX packets 839 bytes 230767 (230.7 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1277 bytes 450307 (450.3 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
At first, the systemd-networkd-wait-online.service service crashed when the server was booting, the download took 5 minutes.
Fixed this by adding the startup parameter
--ignore =(ustname) in /lib/systemd/system/systemd-networkd-wait-online.service.
Without a bridge, the network works fine, but there is no network in the virtual machine. Where did I take a wrong turn?

Answer 1

The virtual machine has its own vif interface and it must connect to the bridge. To assign the address enp031f6 to the bridge, remove all address settings from the interface.