Which of the following is a virtual network function (VNF) device?

A virtual firewall or virtual router is an example of a VNF. These devices are typically network functions that are found in internal networks such as firewalls and routers. These devices perform basic network functionality and run as virtual machines or virtual instances. A virtual switch is not considered a VNF because it is an elemental part of the hypervisor, used for communications. A database server and file server are not functions of a network; they are roles found on servers.