Solved in our case anyway.
Would you believe it if I told you that the cause of our multicasting woes was a PC attached to the network that was
NOT turned on but it
WAS turned on at the wall socket?
There is a little more to it than that, but not much more.
Any PC with an Intel 82566DM-2 card can cause this issue.
When powered down but not off at the wall socket by the card will (by default) drop its connection speed to 10Mbit.
I haven't looked in to why this would cause
every multicast job to run slowly but I guarantee it does (at least in our case).
We spent the whole day testing, and finally proved that this is our issue.
There are two resolutions to this:
- Disconnect the offending PC from the network, either by patch cable or power off at the wall.
- In Windows, the lan connection properties, network card configuration, power saving tab, deselect the tick box by Reduce link speed during standby.
I really hope this helps someone else, we've been scratching our heads about this problem here for months.
-Martin