проблемы с бридж-сетью libvirt на centos 8

Я использую Centos 8 в качестве virt-host с libvirt и kvm / qemu. Сеть установлена ​​в режим моста с помощью virbr0. Внезапно и за ночь это перестает работать: клиенты больше не подключаются, и если я пытаюсь подключить сеть в диспетчере виртуальных машин, я получаю «Bridge virbr0: Пустой мост», и это даже до запуска любого клиента.

[root@labpc1 log]# ifconfig
enp5s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.2.8  netmask 255.255.255.0  broadcast 192.168.2.255
        inet6 2003:c0:3713:3000:fa5b:356b:c6a6:18ff  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::9b26:4d1a:f92c:c21c  prefixlen 64  scopeid 0x20<link>
        ether 34:97:f6:8e:c0:73  txqueuelen 1000  (Ethernet)
        RX packets 4788  bytes 482052 (470.7 KiB)
        RX errors 0  dropped 912  overruns 0  frame 0
        TX packets 2205  bytes 617635 (603.1 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 192.168.2.8  netmask 255.255.255.0  broadcast 192.168.2.255
        ether de:a2:bd:89:f8:d4  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

В / var / log / messages есть сообщения:

grep virbr0 /var/log/messages 
Jan  9 19:24:30 labpc1 NetworkManager[1051]: <info>  [1578594270.5088] ifcfg-rh: new connection /etc/sysconfig/network-scripts/ifcfg-virbr0 (a2d02297-f0a1-4f1e-a5c4-ebd5d5e62c89,"virbr0")
Jan  9 19:24:30 labpc1 NetworkManager[1051]: <info>  [1578594270.5092] ifcfg-rh: new connection /etc/sysconfig/network-scripts/ifcfg-virbr0_slave_1 (7b0e15aa-3c0c-44a6-802e-0a1af319a2e2,"virbr0 slave 1")
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.2427] manager: (virbr0): new Bridge device (/org/freedesktop/NetworkManager/Devices/3)
Jan  9 19:24:31 labpc1 systemd-udevd[1340]: Could not generate persistent MAC address for virbr0: No such file or directory
Jan  9 19:24:31 labpc1 kernel: IPv6: ADDRCONF(NETDEV_UP): virbr0: link is not ready
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.4417] device (virbr0): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.4439] device (virbr0): state change: unavailable -> disconnected (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.4449] policy: auto-activating connection 'virbr0' (a2d02297-f0a1-4f1e-a5c4-ebd5d5e62c89)
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.4455] device (virbr0): Activation: starting connection 'virbr0' (a2d02297-f0a1-4f1e-a5c4-ebd5d5e62c89)
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.4456] device (virbr0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:31 labpc1 NetworkManager[1051]: <info>  [1578594271.4543] device (virbr0): state change: prepare -> config (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:32 labpc1 NetworkManager[1051]: <info>  [1578594272.7065] device (virbr0): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:32 labpc1 NetworkManager[1051]: <info>  [1578594272.7077] device (virbr0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:32 labpc1 kernel: IPv6: ADDRCONF(NETDEV_UP): virbr0: link is not ready
Jan  9 19:24:32 labpc1 avahi-daemon[932]: Joining mDNS multicast group on interface virbr0.IPv4 with address 192.168.2.8.
Jan  9 19:24:32 labpc1 NetworkManager[1051]: <info>  [1578594272.7083] device (virbr0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:32 labpc1 avahi-daemon[932]: New relevant interface virbr0.IPv4 for mDNS.
Jan  9 19:24:32 labpc1 NetworkManager[1051]: <info>  [1578594272.7084] device (virbr0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'managed')
Jan  9 19:24:32 labpc1 avahi-daemon[932]: Registering new address record for 192.168.2.8 on virbr0.IPv4.
Jan  9 19:24:32 labpc1 NetworkManager[1051]: <info>  [1578594272.8032] policy: set 'virbr0' (virbr0) as default for IPv4 routing and DNS
Jan  9 19:24:32 labpc1 NetworkManager[1051]: <info>  [1578594272.8863] device (virbr0): Activation: successful, device activated.
Jan  9 19:24:32 labpc1 nm-dispatcher[1121]: req:3 'up' [virbr0]: new request (3 scripts)
Jan  9 19:24:32 labpc1 nm-dispatcher[1121]: req:3 'up' [virbr0]: start running ordered scripts...

В частности, мне не хватает такого сообщения, как ядро: virbr0: порт 3 (vnet1) перешел в состояние пересылки

Раньше работал без каких-либо преднамеренных изменений ..

Любая подсказка будет высоко оценена

Вольфганг