What is SD-WAN?
Why Interviewers Ask This
Interviewers ask this to evaluate whether you have the depth of knowledge needed to mentor others and lead technical decisions. The expected answer goes beyond definitions into practical implications and real-world consequences.
Answer
SD-WAN (Software-Defined Wide Area Network) applies software-defined networking (SDN) principles to WAN connectivity, separating the control plane from the data plane to centrally manage and optimize WAN traffic. Traditional MPLS WANs are expensive, inflexible, and slow to provision. SD-WAN allows organizations to use multiple transport types (MPLS, broadband Internet, 4G/5G) simultaneously and intelligently route traffic based on application policies. Key capabilities: centralized management (single dashboard for all branches), application-aware routing (route Salesforce over MPLS, YouTube over cheap broadband), built-in encryption (zero-trust overlay network), WAN optimization, and cloud optimization (direct breakout to AWS/Azure instead of backhauling to HQ). Vendors: Cisco Viptela, VMware VeloCloud, Fortinet SD-WAN, Palo Alto Prisma SD-WAN. SD-WAN can reduce WAN costs 30-50% while improving performance.
Common Mistake
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