Yes, It works!  Thank you, Andrea
I cannot turn on the link on the fortygigabit ethernet interfaces between thoose switches. On the S4048 side: Interface fortyGigE 2/49 no ip address mtu 9216 switchport no spanning-tree no shutdown   And the show interfaces command: fortyGigE 2/49 is up, line protocol is down .... Puggable media present, QSFP type is 40GBASE-CR4-5M   On the N4064 side: show run int fo1/0/2 spanning-tree disable  It also recognises the tranceiver as Dell. Any ideas?  
fortygigabit uplink between N4064 and S4048 links in down state