Temporary wim-files for multicast transmissions still needed for WDS installation in Server 2012 R2?

Question

Acording to
https://technet.microsoft.com/en-us/library/dn281955.aspx one of the new features for WDS in Server 2012 R2 for multicast is:
Improved multicast deployment by eliminating the need for making a local copy of the install.wim file. You can apply the install.wim file while it is being downloaded without significant impact to the application process.
However, this doesn't seem to be activated by default and I still get the following error when installing one or more machines using multicast:
"Windows Setup cannot locate a valid hard drive to store temporary installation files." However, once I remove Multicast from this install image, it installs without any problems at all.
I have also noticed that while multicasting, the installation will use the "Copying Windows files" phase, while downloading and copying the install.wim (or whatever name it is) locally on the hard drive first, so this will require lots of space.
So the question is, how do you enable this new feature that should be a part of WDS in Server 2012 R2???

Answer 1

Full version:
Following steps could help enable the feature:
1.       Mount the boot image using dism.
e.g.
>dism /mount-wim /wimfile:c:\remoteinstall\boot\x64\images\boot.wim /index:2 /mountdir:c:\mount
2.       Create a metadata file if no existing one. The metadata file should be in mountdir from the first step under mountdir\sources. And the file name should be: WdsClientMetadata.txt
3.       Add entry to the metadata file: WDS.Client.Multicast.WIM.Streaming.Enabled=true
4.       Save changes and unmount the boot image
e.g.
>dism /unmounts-wim /mountdir:c:\mount /commit
Sorry for the late reply, but I had to test this thoroughly since I didn't get it working right away. I tried both the regedit you first mentioned, and later also creating a textfile in the "/index:2 boot.wim", both without any success. I noticed
that creating the sources\WdsClientMetadata.txt with the data "WDS.Client.Multicast.WIM.Streaming.Enabled=true" gives me an error upon booting into WDS as follows (EUFI/IPv6-boot):
Same happens if I boot using IPv4 (an non-UEFI boot), except that there would be a plain IPv4-address instead in the error msg. Just for troubleshooting I tried writing WDS.Client.Multicast.WIM.Streaming.Enabled=false in the file instead, and WDS would throw
me the exact same error message. Once I delete the file sources\WdsClientMetadata.txt from the WDS/Boot image, the client boots ok, both for IPv4/IPv6. Disabling the firewall on the WDS didn't help, so something in the configuration is still missing? I'm getting
to a dead end here, and I suppose you're all out of advice on this one?
Thank you Shaon Shan for your great effort so far.