In 2012 QEMU added UDP unicast network backend support https://github.com/qemu/qemu/commit/0e0e7facc775e9bb020314f48751b3d09f316... Checked latest libvirt on the git repo, and didn't see this as an option. So tried to use the mcast tunnel mode. I keep getting duplicate packets with BPDUs and LLDP packets going between the Point to point connection between the VMs. VMs have bridges on them. When I used the TCP tunnel interface, if the client came up before the server end, the connection failed to establish. So both methods not super reliable. If I manually change the netdev settings to use unicast udp tunneling the connection is way more stable just like the GNS3 connections. Has anyone written support for UDP unicast network backend for QEMU and the patch is awaiting review? Searched mailing list and couldn't find a bug covering this. Just want to be sure no one has worked on this before creating a patch to add this support.