Hello Umesh
The NFVI as a framework has several components. These components can be separated into two categories: hardware and virtual. Among the hardware components are the Nexus series devices. Nexus devices essentially provide the physical connection to the virtualized NFVI environment. Looking at the diagram below, the nexus switches would fall under the “Hardware Network” component at the bottom right.
This might sound philosophical, but I believe it will clarify some things. We live in a physical world, and the interfaces we require are physical So even if you virtualize a large part of servers and networks, you still need some interface to the physical world to connect those portions of the network that are indeed physical. That’s where the nexus switches come in. They are the physical interface to the NFVI environment.
Only nexus devices support the Cisco NFV infrastructure and that’s why the are mentioned here. You can find out more about it at the following Cisco link:
I hope this has been helpful!
Laz