I'm attempting to script adding a network interface to a centos 6 guest. I know the interface can be set up using the virt-manager gui but it's highly desirable for it to be added as part of an Ansible playbook using virsh attach-interface or alternatively as part of virt-install.

The desired interface should look like this (although with a new mac adress)

<interface type='direct'>
  <mac address='52:54:00:39:f8:3a'/>
  <source dev='enp3s0' mode='bridge'/>
  <target dev='macvtap8'/>
  <model type='virtio'/>
  <alias name='net0'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>

I have been unable to replicate this using virsh attach-interface or virt-install. I've tried using the following

virsh attach-interface 16 --type direct --source enp3s0 --model virtio --config --live

but this, unfortunately, doesn't set the source mode so I end up with the following interface

<interface type='direct'>
  <mac address='52:54:00:e1:d8:2c'/>
  <source dev='enp3s0' mode='vepa'/>
  <target dev='macvtap15'/>
  <model type='virtio'/>
  <alias name='net1'/>
  <address type='pci' domain='0x0000' bus='0x00' slot='0x0a' function='0x0'/>

in an ideal world I would like to be able to do something like

virsh attach-interface 16 --type direct --source enp3s0 --model virtio --mode bridge --config --live

but this returns the following error and I can't find the correct option to specify for this operation.

error: command 'attach-interface' doesn't support option --mode
  • I never use macvtap, but actual Linux bridge. This makes VM setup a bit easier and more reliable, and you don't necessarily have to create a libvirt virtual network either. – Michael Hampton Dec 16 '16 at 15:28

Since you already know the exact XML you want for the NIC, you should just avoid the virsh attach-interface command and instead use virsh attach-device. The attach-device command accepts the full XML document directly for the new device. attach-interface is just a dumb wrapper around attach-device which generates XML for you. So since you have the XML already there's no point in using attach-interface

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