Dell Optiplex 7020: Multicast problem

[mmg]

Hi all,

we’ve been using FOG to set up our PC rooms for many years, running unicast and multicast sessions at full network speed. Now there is a problem with our new Dell Optiplex 7020 SFF machines: Unicast runs at full network speed, but multicast gets stuck after opening the partclone window. A FOG server upgrade to version working-1.6 had no effect.
The PCs have Intel i219-lm NICs.
Our PC rooms are equipped with unmanaged Netgear GS switches. Uplinks go to Cisco switches.
FOG server and PCs are in the same network.
Thanks for any kind of help and ideas!

Manuel