[Bug 1860926] Re: Ubuntu 20.04 Systemd fails to configure bridged network

Dan Streetman ddstreet at canonical.com
Tue Apr 14 12:46:45 UTC 2020 

** Also affects: systemd (Ubuntu Focal)
   Importance: Undecided
       Status: Confirmed

** Changed in: systemd (Ubuntu Focal)
   Importance: Undecided => Critical

** Description changed:

- Freshly installed Ubuntu 20.04 fully patched to days date with static IP
- address works fine and survives a reboot
+ [impact]
+ 
+ A bridged interface with static ipv4 address and gateway configuration
+ will fail to properly add the route via the gateway, leaving the system
+ without a globally working network.
+ 
+ [test case]
+ 
+ On a Focal system, remove all configuration and create this netplan:
  
  network:
-   version: 2
-   renderer: networkd
-   ethernets:
-     enp4s0:
-       dhcp4: false
-       addresses: [192.168.0.4/24]
-       gateway4: 192.168.0.1
-       nameservers:
-         search: [mydomain]
-         addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
+   version: 2
+   renderer: networkd
+   ethernets:
+     enp4s0:
+       dhcp4: false
+   bridges:
+     br0:
+       interfaces: [enp4s0]
+       dhcp4: no
+       addresses: [192.168.0.4/24]
+       gateway4: 192.168.0.1
+       nameservers:
+         search: [mydomain]
+         addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
+ 
+ 
+ Replace the interface name 'enp4s0' with the actual interface name on the test system.
+ 
+ Reboot the system, and check the route to the gateway, which will be
+ missing:
+ 
+ root at lp1860926-f:~# ip r
+ 192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4 
+ 
+ The route is expected to be present, e.g.:
+ 
+ ubuntu at lp1860926-e:~$ ip r
+ default via 192.168.0.1 dev br0 proto static 
+ 192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4 
+ 
+ [regression potential]
+ 
+ TBD
+ 
+ [scope]
+ 
+ This is not reproducable on Eoan or Bionic; this is needed only for
+ Focal.
+ 
+ [original description]
+ 
+ 
+ Freshly installed Ubuntu 20.04 fully patched to days date with static IP address works fine and survives a reboot
+ 
+ network:
+   version: 2
+   renderer: networkd
+   ethernets:
+     enp4s0:
+       dhcp4: false
+       addresses: [192.168.0.4/24]
+       gateway4: 192.168.0.1
+       nameservers:
+         search: [mydomain]
+         addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
  
  however when converted to a bridged network for kvm
  
  network:
-   version: 2
-   renderer: networkd
-   ethernets:
-     enp4s0:
-       dhcp4: false
-   bridges:
-     br0:
-       interfaces: [enp4s0]
-       dhcp4: no
-       addresses: [192.168.0.4/24]
-       gateway4: 192.168.0.1
-       nameservers:
-         search: [mydomain]
-         addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
+   version: 2
+   renderer: networkd
+   ethernets:
+     enp4s0:
+       dhcp4: false
+   bridges:
+     br0:
+       interfaces: [enp4s0]
+       dhcp4: no
+       addresses: [192.168.0.4/24]
+       gateway4: 192.168.0.1
+       nameservers:
+         search: [mydomain]
+         addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
  
  will not survive a reboot and required systemd-network to be restarted or
  @reboot /usr/sbin/netplan apply
  added to the crontab
  
- 
  after a reboot the network can not b eaccseed and a
  systemctl status systemd-networkd produces
  
  systemd-networkd.service - Network Service
-      Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
-      Active: active (running) since Sun 2020-01-26 16:36:28 UTC; 2min 27s ago
+      Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
+      Active: active (running) since Sun 2020-01-26 16:36:28 UTC; 2min 27s ago
  TriggeredBy: ● systemd-networkd.socket
-        Docs: man:systemd-networkd.service(8)
-    Main PID: 979 (systemd-network)
-      Status: "Processing requests..."
-       Tasks: 1 (limit: 57662)
-      Memory: 4.1M
-      CGroup: /system.slice/systemd-networkd.service
-              └─979 /lib/systemd/systemd-networkd
+        Docs: man:systemd-networkd.service(8)
+    Main PID: 979 (systemd-network)
+      Status: "Processing requests..."
+       Tasks: 1 (limit: 57662)
+      Memory: 4.1M
+      CGroup: /system.slice/systemd-networkd.service
+              └─979 /lib/systemd/systemd-networkd
  
  Jan 26 16:38:02 firebolt systemd-networkd[979]: rtnl: received neighbor for link '5' we don't know about, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link DOWN
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Lost carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Kernel removed an address we don't remember: fe80::5054:ff:fed9:7e26/64 (valid forever), ignoring.
  
- 
- systemctl restart systemd-networkd resolved the issue and a 
+ systemctl restart systemd-networkd resolved the issue and a
  
  systemctl status systemd-network producessystemd-networkd.service - Network Service
-      Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
-      Active: active (running) since Sun 2020-01-26 16:39:28 UTC; 41s ago
+      Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
+      Active: active (running) since Sun 2020-01-26 16:39:28 UTC; 41s ago
  TriggeredBy: ● systemd-networkd.socket
-        Docs: man:systemd-networkd.service(8)
-    Main PID: 1650 (systemd-network)
-      Status: "Processing requests..."
-       Tasks: 1 (limit: 57662)
-      Memory: 1.6M
-      CGroup: /system.slice/systemd-networkd.service
-              └─1650 /lib/systemd/systemd-networkd
+        Docs: man:systemd-networkd.service(8)
+    Main PID: 1650 (systemd-network)
+      Status: "Processing requests..."
+       Tasks: 1 (limit: 57662)
+      Memory: 1.6M
+      CGroup: /system.slice/systemd-networkd.service
+              └─1650 /lib/systemd/systemd-networkd
  
  Jan 26 16:39:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev ready
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: Gained IPv6LL
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: Enumeration completed
  Jan 26 16:39:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev exists, using existing without changing its parameters
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: IPv6 successfully enabled
- 
  
  a journalctl -u systemd-network produces
  
  Jan 26 16:36:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: netdev ready
  Jan 26 16:36:28 firebolt systemd-networkd[979]: Enumeration completed
  Jan 26 16:36:28 firebolt systemd-networkd[979]: wlp3s0: Interface name change detected, wlp3s0 has been renamed to wlan0.
  Jan 26 16:36:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: wlan0: Interface name change detected, wlan0 has been renamed to wlp3s0.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: IPv6 successfully enabled
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Link UP
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Lost carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: Link UP
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Could not set route: Network is unreachable
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Failed
  Jan 26 16:36:30 firebolt systemd-networkd[979]: br0: Lost carrier
  Jan 26 16:36:31 firebolt systemd-networkd[979]: enp4s0: Gained carrier
  Jan 26 16:36:31 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: rtnl: received neighbor for link '5' we don't know about, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link DOWN
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Lost carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Kernel removed an address we don't remember: fe80::5054:ff:fed9:7e26/64 (valid forever), ignoring.
  Jan 26 16:39:28 firebolt systemd[1]: Stopping Network Service...
  Jan 26 16:39:28 firebolt systemd[1]: systemd-networkd.service: Succeeded.
  Jan 26 16:39:28 firebolt systemd[1]: Stopped Network Service.
  Jan 26 16:39:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev ready
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: Gained IPv6LL
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: Enumeration completed
  Jan 26 16:39:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev exists, using existing without changing its parameters
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: IPv6 successfully enabled
  
- 
  the network should restart properly after a reboot liek in earlier
  version of ubuntu 18.04 for example

** Description changed:

  [impact]
  
  A bridged interface with static ipv4 address and gateway configuration
  will fail to properly add the route via the gateway, leaving the system
  without a globally working network.
  
  [test case]
  
  On a Focal system, remove all configuration and create this netplan:
  
  network:
    version: 2
    renderer: networkd
    ethernets:
      enp4s0:
        dhcp4: false
    bridges:
      br0:
        interfaces: [enp4s0]
        dhcp4: no
        addresses: [192.168.0.4/24]
        gateway4: 192.168.0.1
        nameservers:
          search: [mydomain]
          addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
  
- 
- Replace the interface name 'enp4s0' with the actual interface name on the test system.
+ Replace the interface name 'enp4s0' with the actual interface name on
+ the test system.
  
  Reboot the system, and check the route to the gateway, which will be
  missing:
  
  root at lp1860926-f:~# ip r
- 192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4 
+ 192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4
  
  The route is expected to be present, e.g.:
  
  ubuntu at lp1860926-e:~$ ip r
- default via 192.168.0.1 dev br0 proto static 
- 192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4 
+ default via 192.168.0.1 dev br0 proto static
+ 192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4
  
  [regression potential]
  
- TBD
+ Not SRU - N/A
  
  [scope]
  
  This is not reproducable on Eoan or Bionic; this is needed only for
  Focal.
  
  [original description]
  
- 
- Freshly installed Ubuntu 20.04 fully patched to days date with static IP address works fine and survives a reboot
+ Freshly installed Ubuntu 20.04 fully patched to days date with static IP
+ address works fine and survives a reboot
  
  network:
    version: 2
    renderer: networkd
    ethernets:
      enp4s0:
        dhcp4: false
        addresses: [192.168.0.4/24]
        gateway4: 192.168.0.1
        nameservers:
          search: [mydomain]
          addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
  
  however when converted to a bridged network for kvm
  
  network:
    version: 2
    renderer: networkd
    ethernets:
      enp4s0:
        dhcp4: false
    bridges:
      br0:
        interfaces: [enp4s0]
        dhcp4: no
        addresses: [192.168.0.4/24]
        gateway4: 192.168.0.1
        nameservers:
          search: [mydomain]
          addresses: [192.168.0.1,192.168.0.2,192.168.0.3]
  
  will not survive a reboot and required systemd-network to be restarted or
  @reboot /usr/sbin/netplan apply
  added to the crontab
  
  after a reboot the network can not b eaccseed and a
  systemctl status systemd-networkd produces
  
  systemd-networkd.service - Network Service
       Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
       Active: active (running) since Sun 2020-01-26 16:36:28 UTC; 2min 27s ago
  TriggeredBy: ● systemd-networkd.socket
         Docs: man:systemd-networkd.service(8)
     Main PID: 979 (systemd-network)
       Status: "Processing requests..."
        Tasks: 1 (limit: 57662)
       Memory: 4.1M
       CGroup: /system.slice/systemd-networkd.service
               └─979 /lib/systemd/systemd-networkd
  
  Jan 26 16:38:02 firebolt systemd-networkd[979]: rtnl: received neighbor for link '5' we don't know about, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link DOWN
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Lost carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Kernel removed an address we don't remember: fe80::5054:ff:fed9:7e26/64 (valid forever), ignoring.
  
  systemctl restart systemd-networkd resolved the issue and a
  
  systemctl status systemd-network producessystemd-networkd.service - Network Service
       Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
       Active: active (running) since Sun 2020-01-26 16:39:28 UTC; 41s ago
  TriggeredBy: ● systemd-networkd.socket
         Docs: man:systemd-networkd.service(8)
     Main PID: 1650 (systemd-network)
       Status: "Processing requests..."
        Tasks: 1 (limit: 57662)
       Memory: 1.6M
       CGroup: /system.slice/systemd-networkd.service
               └─1650 /lib/systemd/systemd-networkd
  
  Jan 26 16:39:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev ready
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: Gained IPv6LL
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: Enumeration completed
  Jan 26 16:39:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev exists, using existing without changing its parameters
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: IPv6 successfully enabled
  
  a journalctl -u systemd-network produces
  
  Jan 26 16:36:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: netdev ready
  Jan 26 16:36:28 firebolt systemd-networkd[979]: Enumeration completed
  Jan 26 16:36:28 firebolt systemd-networkd[979]: wlp3s0: Interface name change detected, wlp3s0 has been renamed to wlan0.
  Jan 26 16:36:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: wlan0: Interface name change detected, wlan0 has been renamed to wlp3s0.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: IPv6 successfully enabled
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Link UP
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Lost carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: Link UP
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Could not set route: Network is unreachable
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Failed
  Jan 26 16:36:30 firebolt systemd-networkd[979]: br0: Lost carrier
  Jan 26 16:36:31 firebolt systemd-networkd[979]: enp4s0: Gained carrier
  Jan 26 16:36:31 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: rtnl: received neighbor for link '5' we don't know about, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link DOWN
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Lost carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Kernel removed an address we don't remember: fe80::5054:ff:fed9:7e26/64 (valid forever), ignoring.
  Jan 26 16:39:28 firebolt systemd[1]: Stopping Network Service...
  Jan 26 16:39:28 firebolt systemd[1]: systemd-networkd.service: Succeeded.
  Jan 26 16:39:28 firebolt systemd[1]: Stopped Network Service.
  Jan 26 16:39:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev ready
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: Gained IPv6LL
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: Enumeration completed
  Jan 26 16:39:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev exists, using existing without changing its parameters
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: IPv6 successfully enabled
  
  the network should restart properly after a reboot liek in earlier
  version of ubuntu 18.04 for example

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https://bugs.launchpad.net/bugs/1860926

Title:
  Ubuntu 20.04  Systemd fails to configure bridged network

Status in systemd package in Ubuntu:
  Confirmed
Status in systemd source package in Focal:
  Confirmed

Bug description:
  [impact]

  A bridged interface with static ipv4 address and gateway configuration
  will fail to properly add the route via the gateway, leaving the
  system without a globally working network.

  [test case]

  On a Focal system, remove all configuration and create this netplan:

  network:
    version: 2
    renderer: networkd
    ethernets:
      enp4s0:
        dhcp4: false
    bridges:
      br0:
        interfaces: [enp4s0]
        dhcp4: no
        addresses: [192.168.0.4/24]
        gateway4: 192.168.0.1
        nameservers:
          search: [mydomain]
          addresses: [192.168.0.1,192.168.0.2,192.168.0.3]

  Replace the interface name 'enp4s0' with the actual interface name on
  the test system.

  Reboot the system, and check the route to the gateway, which will be
  missing:

  root at lp1860926-f:~# ip r
  192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4

  The route is expected to be present, e.g.:

  ubuntu at lp1860926-e:~$ ip r
  default via 192.168.0.1 dev br0 proto static
  192.168.0.0/24 dev br0 proto kernel scope link src 192.168.0.4

  [regression potential]

  Not SRU - N/A

  [scope]

  This is not reproducable on Eoan or Bionic; this is needed only for
  Focal.

  [original description]

  Freshly installed Ubuntu 20.04 fully patched to days date with static
  IP address works fine and survives a reboot

  network:
    version: 2
    renderer: networkd
    ethernets:
      enp4s0:
        dhcp4: false
        addresses: [192.168.0.4/24]
        gateway4: 192.168.0.1
        nameservers:
          search: [mydomain]
          addresses: [192.168.0.1,192.168.0.2,192.168.0.3]

  however when converted to a bridged network for kvm

  network:
    version: 2
    renderer: networkd
    ethernets:
      enp4s0:
        dhcp4: false
    bridges:
      br0:
        interfaces: [enp4s0]
        dhcp4: no
        addresses: [192.168.0.4/24]
        gateway4: 192.168.0.1
        nameservers:
          search: [mydomain]
          addresses: [192.168.0.1,192.168.0.2,192.168.0.3]

  will not survive a reboot and required systemd-network to be restarted or
  @reboot /usr/sbin/netplan apply
  added to the crontab

  after a reboot the network can not b eaccseed and a
  systemctl status systemd-networkd produces

  systemd-networkd.service - Network Service
       Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
       Active: active (running) since Sun 2020-01-26 16:36:28 UTC; 2min 27s ago
  TriggeredBy: ● systemd-networkd.socket
         Docs: man:systemd-networkd.service(8)
     Main PID: 979 (systemd-network)
       Status: "Processing requests..."
        Tasks: 1 (limit: 57662)
       Memory: 4.1M
       CGroup: /system.slice/systemd-networkd.service
               └─979 /lib/systemd/systemd-networkd

  Jan 26 16:38:02 firebolt systemd-networkd[979]: rtnl: received neighbor for link '5' we don't know about, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link DOWN
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Lost carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Kernel removed an address we don't remember: fe80::5054:ff:fed9:7e26/64 (valid forever), ignoring.

  systemctl restart systemd-networkd resolved the issue and a

  systemctl status systemd-network producessystemd-networkd.service - Network Service
       Loaded: loaded (/lib/systemd/system/systemd-networkd.service; enabled; vendor preset: enabled)
       Active: active (running) since Sun 2020-01-26 16:39:28 UTC; 41s ago
  TriggeredBy: ● systemd-networkd.socket
         Docs: man:systemd-networkd.service(8)
     Main PID: 1650 (systemd-network)
       Status: "Processing requests..."
        Tasks: 1 (limit: 57662)
       Memory: 1.6M
       CGroup: /system.slice/systemd-networkd.service
               └─1650 /lib/systemd/systemd-networkd

  Jan 26 16:39:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev ready
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: Gained IPv6LL
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: Enumeration completed
  Jan 26 16:39:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev exists, using existing without changing its parameters
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: IPv6 successfully enabled

  a journalctl -u systemd-network produces

  Jan 26 16:36:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: netdev ready
  Jan 26 16:36:28 firebolt systemd-networkd[979]: Enumeration completed
  Jan 26 16:36:28 firebolt systemd-networkd[979]: wlp3s0: Interface name change detected, wlp3s0 has been renamed to wlan0.
  Jan 26 16:36:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: wlan0: Interface name change detected, wlan0 has been renamed to wlp3s0.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: IPv6 successfully enabled
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Link UP
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Lost carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: enp4s0: Link UP
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Could not set route: Network is unreachable
  Jan 26 16:36:28 firebolt systemd-networkd[979]: br0: Failed
  Jan 26 16:36:30 firebolt systemd-networkd[979]: br0: Lost carrier
  Jan 26 16:36:31 firebolt systemd-networkd[979]: enp4s0: Gained carrier
  Jan 26 16:36:31 firebolt systemd-networkd[979]: br0: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: rtnl: received neighbor for link '5' we don't know about, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: rtnl: received neighbor message with invalid family, ignoring.
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Gained carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0: Link UP
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Link DOWN
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Lost carrier
  Jan 26 16:38:02 firebolt systemd-networkd[979]: virbr0-nic: Kernel removed an address we don't remember: fe80::5054:ff:fed9:7e26/64 (valid forever), ignoring.
  Jan 26 16:39:28 firebolt systemd[1]: Stopping Network Service...
  Jan 26 16:39:28 firebolt systemd[1]: systemd-networkd.service: Succeeded.
  Jan 26 16:39:28 firebolt systemd[1]: Stopped Network Service.
  Jan 26 16:39:28 firebolt systemd[1]: Starting Network Service...
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev ready
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: Gained IPv6LL
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: Enumeration completed
  Jan 26 16:39:28 firebolt systemd[1]: Started Network Service.
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: netdev exists, using existing without changing its parameters
  Jan 26 16:39:28 firebolt systemd-networkd[1650]: br0: IPv6 successfully enabled

  the network should restart properly after a reboot liek in earlier
  version of ubuntu 18.04 for example

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