PTP client joins multicast group only on loopback interface.

[JackGarbiec]

Hi,
As many others I've had some issues getting multicast to work on the windows PTP client, I eventually ended up going with something else as the current native client seems under-baked, but I thought I'll report the issue and my workaround.
On msdn the only documented setting for enabling multicast communication is:
EnableMulticastRx=1
This wasn't enough for my machine to start receiving announce messages.
netsh interface ip show joins showed that my machine was subscribed to the ptp multicast addresses 224.0.1.129 & 224.0.0.107 on 'Loopback Pseudo-Interface'. Hence ptp could never receive messages, my GM was reachable only through the ethernet interface.
Adding a key ChosenMcastIfIpAddr=ip_addr_of_my_ethernet_interface and restarting the time service solved the issue.
Now for some reason this reg key is not mentioned on MSDN ptp article, i was only able to find it by looking at w32time logs, so I assume the client is supposed to either subscribe to that group on all interfaces or figure it out in some other way, but clearly it's not doing that, at least in my case.