In vSphere 5.5 and later, both the physical function (PF) and virtual functions (VFs) of an SR-IOV capable physical adapter can be configured to handle virtual machine traffic.
The PF of an SR-IOV physical adapter controls the VFs that virtual machines use, and can carry the traffic flowing through the standard or distributed switch that handles the networking of these SR-IOV enabled virtual machines.
The SR-IOV physical adapter works in different modes depending on whether it backs the traffic of the switch.
Mixed Mode
The physical adapter provides virtual functions to virtual machines attached to the switch and directly handles traffic from non SR-IOV virtual machines on the switch.
You can check whether an SR-IOV physical adapter is in mixed mode in the topology diagram of the switch. An SR-IOV physical adapter in mixed mode appears with the 
icon in the list of physical adapters for a standard switch or in the list of uplink group adapters for a distributed switch.
SR-IOV Only Mode
The physical adapter provides virtual functions to virtual machines connected to a virtual switch, but does not back traffic from non SR-IOV virtual machines on the switch.
To verify whether the physical adapter is in SR-IOV only mode, examine the topology diagram of the switch. In this mode, the physical adapter is in a separate list called External SR-IOV Adapters and appears with the 
icon.
Non SR-IOV Mode
The physical adapter is not used for traffic related to VF aware virtual machines. It handles traffic from non SR-IOV virtual machines only.
