I've realized that there is no  "dot1x mac-auth-bypass" option in the interface configuration  in current Dell N2048  switches firmware (both 6.5.1.3 and 6.5.1.5). I've used this feature  in 6.3.0.18 version to use mac based dynamic vlan assignment. Can somebody tell me what is the current equivalent of this command ?

interface Gi1/0/12
    switchport mode general
    dot1x port-control mac-based
    dot1x reauthentication
    dot1x mac-auth-bypass
    authentication order mab

Now I can't authenticate the client (NIC) on radius server and therefore switch cannot assign the right vlan to the port.

thx for any help
Markus