300-420 Question #18: Real Exam Question with Answer & Explanation

Question

Which solution allows overlay VNs to communicate with each other in an SD-WAN Architecture?

Options

• AExternal fusion routers can be used to map VNs to VRFs and selectively route traffic between
• BGRE tunneling can be configured between fabric edges to connect one VN to another.
• CSGTs can be used to permit traffic from one VN to another.
• DRoute leaking can be used on the fabric border nodes to inject routes from one VN to another.

Explanation

{"question_number": 10, "question": "Which solution allows overlay VNs to communicate with each other in an SD-WAN Architecture?", "correct_answer": "A. External fusion routers can be used to map VNs to VRFs and selectively route traffic between them.", "explanation": "In Cisco SD-WAN (and SD-Access), Virtual Networks (VNs) are logically isolated segments, each mapped to a VRF. By default, traffic cannot cross VN boundaries. External fusion routers (or firewall/service nodes acting as fusion devices) are the Cisco-recommended method to enable inter-VN communication: they connect to multiple VRFs (one per VN) and selectively route or policy-filter traffic between them, often integrating with a firewall for security enforcement. GRE tunneling between fabric edges (B) is not a standard inter-VN mechanism in SD-WAN. SGTs (C) are Cisco TrustSec tags used for policy enforcement within a domain, not for routing between VNs. Route leaking on border nodes (D) is a valid technique in SD-Access for connecting Guest or shared-service VNs, but the primary and most flexible inter-VN design uses external fusion routers, making A the best answer.", "generated_by": "claude-sonnet", "llm_judge_score": 4}

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