If you choose the Configuration Migration mode, you may need to create a layer-2 bridge between NSX-V and NSX.
Starting with NSX 4.0.1.1, you can also choose the Configuration and Edge Migration mode. This step (creating a layer-2 bridge) is not needed if you choose that mode.
For information on creating a layer-2 bridge between NSX-V and NSX, see Preparing Layer-2 Bridging for Lift-and-Shift Migration.