Planning to implement PIMG device to integrate legacy system.
Debating if we need QOS for the link between the PIMG device to Unity. Unity is on a QOS subnet along with CCM. PIMG device is not on a QOS switch/subnet.
It would make life a lot easier if the PIMG was on the same subnet, switch. Otherwise, if it is on another subnet, same rules apply for voice... VLAN, QOS, trust, etc to the Unity server.
I have (3) PIMGs connecting a legacy pbx and then CCM on the other side as I migrate people. I kept it all on the same subnet and no problems as of yet.... knock on wood.