This post is for folks interested in using libvirt on Linux for building Cumulus test topologies.
Recently libvirt and vagrant-libvirt provider was updated to support QEMU's UDP unicast tunnel mode support. This is the tech used to stitch virtual interfaces in a point-2-point manner reliably. This tech was added to QEMU by the GNS3 folks in 2012.
I created a vagrant libvirt setup that reproduces exactly the Cumulus workbench environment.
In the README I show how to run the Cumulus cldemos in this virtual environment.
Pull requests, comments are always welcome.