Create a NIC without an IP and watch stuff break

Latest response

The GUI allows for creation of networks on cluster level, to which you can attach a NIC. It is not needed to define an IP for this NIC. Not adding an IP to an interface is a valid option in the menu: you can choose "None" for "Boot Protocol" when adding a NIC to a logical network.

 

But when I attach VM's to this network and try to start them, stuff breaks:

 

Thread-120::DEBUG::2012-11-16 12:46:21,763::vm::607::vm.Vm::(_startUnderlyingVm) vmId=`8b982672-1ca8-488b-a112-dcd0a7f8bc15`::_ongoingCreations released
Thread-120::ERROR::2012-11-16 12:46:21,764::vm::631::vm.Vm::(_startUnderlyingVm) vmId=`8b982672-1ca8-488b-a112-dcd0a7f8bc15`::The vm start process failed
Traceback (most recent call last):
  File "/usr/share/vdsm/vm.py", line 597, in _startUnderlyingVm
  File "/usr/share/vdsm/libvirtvm.py", line 1416, in _run
  File "/usr/lib64/python2.6/site-packages/vdsm/libvirtconnection.py", line 83, in wrapper
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 2490, in createXML
libvirtError: XML error: listen network 'vdsm-vm_only_network' had no usable address

 

Anyone else seeing this? My network is called 'vm_only_network'. I does not matter whether this network is or isn't the display network.

Responses

This supposed to work unless there is something I'm missing.
 
Are you sure this is not set as your display network? it looks like libvirt tries to open a socket on this IP, which only means it is a display.
 
Could you please paste here the VM invocation command from the log? We'll be able to see what the VM tries to listen on. 

I'm pretty sure I tested both as display network and not display network. But I'll check this again when I rebuild my environment for the next demo.

 

By the way, if having an IP on a display network (which makes sense) is a requirement, shouldn't bringing up this network without an IP fail?

 

Thanks! :)

 

"By the way, if having an IP on a display network (which makes sense) is a requirement, shouldn't bringing up this network without an IP fail"

 

Indeed, however RHEV Manager allows for changing this network or allowing to select any network after they've been set up on the hosts as a display network. And what about DHCP? It may still fail. So blocking is not trivial. Like any other networking configuration it should be carefully planned. What needs to be done is to assist you, the user, to easily understand what is missing in your configuration. For this specific case, the manager should prevent running a virtual machine on a host that can't identify its display IP by setting the host to non operational with the proper reason -> 'IP is not set on the display network'

 

Could you please open a case with Red Hat support to fix that?

I would, but I'm on a partner NFR and as such cannot open a support case. Filing a bug against RHEV is also a no-go. I would be happy to fill in the blanks if you open a RHEV bug for me though :)

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