What is network function virtualization (NFV)?
Why Interviewers Ask This
Senior Networking engineers are expected to reason about architecture, performance, and edge cases. This question separates mid-level from senior candidates by testing deep system-level understanding.
Answer
NFV (Network Function Virtualization) replaces dedicated hardware appliances (firewalls, load balancers, routers, IDS/IPS) with software running on standard commercial off-the-shelf (COTS) x86 servers and hypervisors. Instead of buying a dedicated Cisco ASA firewall, you run a virtual firewall (vFW) as a VM or container. ETSI defined the NFV architecture with: VNFs (Virtual Network Functions) — the virtualized network appliances, NFVI (NFV Infrastructure) — compute, storage, networking (cloud/hypervisor layer), and MANO (Management and Orchestration) — lifecycle management of VNFs (OpenStack, Kubernetes). Benefits: reduced hardware costs, faster service deployment, elastic scaling (scale up/down based on demand), vendor independence, and simplified management. NFV is used by telecom operators for 5G core networks, virtual CPE (customer premises equipment), and virtual EPC. Closely related to SDN — together they form the foundation of modern carrier networks.
Pro Tip
Demonstrate both theoretical understanding and practical experience. Say what it is, then give an example of how you actually used it in a Networking codebase.