300-420 Question #139: Real Exam Question with Answer & Explanation

Question

A customer requests a VPN solution to connect multiple sites with the company headquarters. All the sites use the same IP subnet. The engineer plans to use VPLS. Which solutions must the engineer include in the design?

Options

• A802.1Q connectivity on the LAN side of the CE
• Broute exchange with the service provider
• Caddress translation to hide overlapping subnets
• Ddifferent VLANs on each site

Explanation

{"question_number": 8, "question": "A customer requests a VPN solution to connect multiple sites with the company headquarters. All the sites use the same IP subnet. The engineer plans to use VPLS.", "correct_answer": "C", "explanation": "VPLS (Virtual Private LAN Service) is a Layer 2 MPLS-based VPN technology that emulates an Ethernet LAN across the service provider network. Because it operates at Layer 2, it does not resolve IP address conflicts - it simply bridges Ethernet frames between sites. When all sites share the same IP subnet, there will be IP address duplication, causing traffic to be delivered to the wrong host or dropped. Therefore, NAT (Network Address Translation) must be used to translate overlapping addresses at each site boundary. Option A (802.1Q trunking) relates to VLAN tagging and does not solve IP overlap. Option B (route exchange with SP) is not required for VPLS, which is a Layer 2 service. Option D (different VLANs per site) does not resolve IP address duplication - overlapping IPs on different VLANs still conflict when bridged over VPLS.", "generated_by": "claude-sonnet", "llm_judge_score": 3}

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