I've been trying to get multicast deployment working in our environment. I notice when I begin the MDT task sequence, the client attempts multicast transfer but always kicks back to unicast. When I run the task sequence on a VM on the same Hyper V host as the MDT server, multicast transfer works just as it should.
We use a Cisco Meraki MX100 for routing on this portion of our network. According to Meraki documentation, "MX Security Appliances will forward IGMP traffic for a single broadcast domain. It does not forward multicast traffic upstream, between VLANs, or over a VPN." So it looks like multicasting across VLANs is a no-go. But I can't get multicast even to work when both the MDT/WDS server and host are on the same VLAN. The ONLY time multicast works is when the host is a VM on the same Hypervisor host.
For reference, I have configured our MDT/WDS server according to the steps defined here: https://keithga.wordpress.com/2014/04/23/multicasting-with-mdt/
Does anyone have any insight on why this might be, or just how the IGMP multicast process works as far as MDT is concerned?