NFV comes with some challenges that require considerations before implementing in existing networks. In large-scale networks, redundancy is a vital characteristic that is essential in order to minimize the downtime of the network if any network element goes down.

With NFV, the deployment should have redundancy at the physical level as well as the virtualized level. For instance, if the redundant switch is hosted on the same physical infrastructure, in the case of a power outage, both switches will fail, leading to a loss of connectivity.

Physical resources required to support a fully virtualized environment are limited. A physical host that supports multiple switch instances will require a network interface card of up to 100 Gbps for optimum functionality. The cost of such hardware to support a fully virtualized environment is on the high side.