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Reference: KVM Networks

This will be a short write up on how to configure the networks I defined in The Crux write up.  It should apply for most "bridge" centric builds.  This is just more of a companion reference.

Virtual Machine Network Configuration (Install)

When creating a virtual machine on the CLI or if like me you create small script files and use virt-install, 

virt-install \
--name sweetname \
--description "Awesome Rocky Server" \
--ram 16384 \
--disk path=/vsto/machines/sweetname.img,size=120 \
--cpu host \
--vcpus=4 \
--cpuset=auto \
--os-variant=rocky8.6 \
--accelerate \
--network bridge:br0 \
--graphics vnc,listen=0.0.0.0 \
--video virtio \
--cdrom /sto/vm/images/rocky-minimal.iso

The network line "--network bridge:br0" should be modified to use the new OVS bridge networks.  From my testing if your configuring for a OVS bridge network that was setup on a access port (untagged port), then it does not appear to matter if you identify the type as either bridge or network.  For example,

# BRIDGE
--network bridge:ovs1

# NETWORK
--network network:ovs1

The resulting XML that is created for the virtual machine (or 'domain' as they call it), does reflect your choice.  So your 'interface' section of the XML could look like these examples,

# BRIDGE
    <interface type='bridge'>
      <source bridge='ovs1'/>
    </interface>

# NETWORK
    <interface type='network'>
      <source network='ovs1'/>
    </interface>

Either method appears to work.

However, when using a OVS bridge network that was setup on a trunk port (tagged port).  We do need to use the network type, because we also need to identify the portgroup of the VLANs that were defined.  In this case we would configure like so,

# NETWORK WITH VLAN
--network network:ovs3,portgroup=ext0

The XML for this configuration would look like this,

# NETWORK WITH VLAN
    <interface type='network'>
      <source network='ovs3' portgroup='ext0'/>
    </interface>

This configuration will put your machine on the specified VLAN.

However again, you can also define the VLAN networks within KVM, so you can just call the VLAN name.  The configurations page shows both options being used.

 

Another option that can be added to the network configure line (there is actually a lot that can be configuredconfigured, but for the sake of this write up, I am sticking to options that pertain to OVS and will make things work) is virtualport_type=openvswitch. 
This option specifically tells the KVM system that this port is part of the OVS network.  I am not sure of all the implications for using this option or not using it.  However, I do like the idea of telling the configuration that it should use the OVS networks, and not something that could be configured elsewhere.  This adds the following to the XML,

# ACCESS PORT (UNTAGGED) NETWORK
<interface type='network'>
      <source network='ovs1'/>
      <virtualport type='openvswitch'>
        <parameters interfaceid='xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'/>
      </virtualport>
    </interface>

# TRUNK (TAGGED) NETWORK WITH VLAN (PORTGROUP)
    <interface type='network'>
      <source network='ovs3' portgroup='ext0'/>
      <virtualport type='openvswitch'>
        <parameters interfaceid='xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'/>
      </virtualport>
    </interface>

For me, I prefer to use the network type for all my configurations and I also tag on the virtualport_type.  This just allows for consistency (at least until I deep dive and fully understand all options and their purposes).

To sum up the install configuration for OVS networks, the following options work,

# ACCESS PORT (UNTAGGED) NETWORK
--network network:ovs1,virtualport_type=openvswitch

# TRUNK (TAGGED) NETWORK WITH VLAN (PORTGROUP)
--network network:ovs3,portgroup=ext0,virtualport_type=openvswitch

Virtual Machine Network Configuration (Post Install)

Above I have already shown examples of the XML that is created when creating a virtual machine.  Here I will show how to modify those setting after a virtual machine is created or for existing machines that will be added to a OVS network.

BACKUP WARNING!
Create a backup of your virtual machines XML file before making any changes.  Just in case something goes sideways.
virsh dumpxml vm-name > vm-name.xml

TIME SAVER TIP!
Before shutting down your VM and changing your network settings within the XML.  Change the IP information on your VM first so after saving your changes and starting your machine, it will come up on the new network.

First off you will want the virtual machine turned off.  The XML of virtual machines are live and get edits when the machines are turned on.  So to make a configuration stick (persistent), you will want to shut the machine down.

# GRACEFUL SHUTDOWN
virsh shutdown <vm name>

# FORCE SHUTDOWN
virsh destroy <vm name>

After the machine is shutdown we can edit the machines XML with the following,

virsh edit <vm name>

The editor will use what is set as your systems default editor, or will default to using the VI editor.  

Comb down through the XML config until you locate the <interface> element.

If the machine used a bridge that was setup prior to having OVS, the configuration may look like the following,

    <interface type='bridge'>
      <mac address='xx:xx:xx:xx:xx:xx'/>
      <source bridge='br0'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>

We will want to modify the interface type within the element, the source, and also add the virtualport type.  Like so,

    <interface type='network'>
      <mac address='xx:xx:xx:xx:xx:xx'/>
      <source network='ovs1'/>
      <virtualport type='openvswitch'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>

This config example is using the "ovs1" network from The Crux write up.  This network is connected to a access port (untagged), on my switch.  So it does not require adding a portgroup (vlan) to the configuration.

Changing the network to a trunk port (tagged) and specifying the vlan (portgroup), is done the same way.  We just need to add the portgroup to the source element.  This example will use the "ovs3" network from The Crux write up, and the "ext0" vlan.

    <interface type='network'>
      <mac address='xx:xx:xx:xx:xx:xx'/>
      <source network='ovs3' portgroup='ext0'/>
      <virtualport type='openvswitch'/>
      <model type='virtio'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>

Once that is complete, save the XML and turn your machine back on,

virsh start <vm name>

That's it!

Hope this helps, and perhaps adds a little knowledge to your arsenal.  :)

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