A BVI is a virtual interface within the switch router that acts like a normal routed interface. A BVI does not support bridging, but it actually represents the corresponding bridge group to routed interfaces within the switch router.
Yes,in your real interface you need to put bridge-group number.
An example of its use is in irb.using this you can route a given protocol between routed interfaces and bridge groups within a single switch router.In case of irb,you need not to give bridge-group cmd under the real routed interface.
