I set up an Ubuntu 16.04 VM in my server a few months ago and every few weeks or so it will have an issue where the IPv4 network seems to disappear.  When this happens I can no longer access the VM via SSH or XRDP (more normal methods) but I can still get in using the noVNC through the web UI.  When I get in I do an ifconfig and I see that the line with the IPv4 info is missing.  Normally I would restart the VM but last time I issued the command "sudo service network-manager restart".  That brought it back.

 

I am currently using a DHCP connection.

 

Anyone have any suggestions on how to fix this?  Should I try a statically assigned IP instead?

what virtual nic are you using? if you are using vmxnet3, switch to something else.

Where do I find that info - here is a cut and paste from my xml file - I didn't change anything as I just used the defaults when I built the VM.

 

    <interface type='bridge'>
      <mac address='52:54:00:8f:42:1f'/>
      <source bridge='br0'/>
      <target dev='vnet0'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x01' function='0x0'/>
    </interface>

 

it' using the virtio driver, which should be fine. though you could try switching to

<model type='e1000-82545em'/>

to rule out an emulated card problem between the vm and the bridge.

 

 

other option is to assign it a static ip in the vm and on your router.

Thanks - for now I have set a static IP in the vm by putting an entry in the /etc/network/interfaces file.  When did you start using funky adapter names like enp2s1 rather than eth0?

 

I will give this a while and see if it behaves now.  When you set a static IP in the network config you don't have to change anything in the router do you?  The static Ip that I have set is outside of my HDCP range.