So connected Port 6 of dlink to port 6 of Dax.
Port 7 of dlink to port 6 of smc. Port 7 of dax to port 7 of smc
It seems that the way you have connected the switches, you are creating a loop, which can result in "broadcast storms" / packets looping around forever.
Search for info on spanning tree protocol, and see if this is part of your problem.
Regards Shahed,