Interesting. We use 2012 as a hyper-V host. Our DC and DHCP (and DNS) are a 2k12 guest. FOG is an ubuntu guest. No issues for us. 2k12 “66” is an IP address (of the fog guest) 2k12 “67” is pxelinux.0 NFS for fog (mounted) storage is hosted on a openfiler NAS external to the VM
No issues for us. Do you use WDS or SCCM ? They both have PXE options which could muddy things.
As an aside, your hyper-v host is your gateway?