Hi Cyril,
Thanks for the reply.
It seems that your tuto is for connecting two Macs together witch wasn't really my issue but I gave it a try after exchanging with Marnix from VSL (it was about forcing connexion speed to 1000 base T on manual witch I did plus chaging MTU to jumbo (9000) but it didn't help the CPU usage on VEPro to drop to 0% and to cut the sound).
So I connected my slave I-mac directly to the second ethrnet port of my Mac Pro and enter manually the new DHCP adress witch is a new one.
At first it seems to work but then I tried with my orchetsral template and even if the issue apear less frequently it stills drop the CPU usage to 0% etc...strangely enough this doesn't happen when I export audio in non-realtime mode !
so I guess we are in the right direction but still some way to go...I hope the VSL support can get back to me (they stoped suddenly to reply).
Another thing that your setup disturbes me for is that I canot connect a third slave witch I do sometimes with my MacBook Pro for some big project...do you think I can turnaround that DHCP adress without using the twoo port of the Mac pro ?
Thank you anyway this was interesting and going in the right direction ;-)
Regards
Stephane