350-401 Question #462: Real Exam Question with Answer & Explanation

Question

What is a consideration when designing a Cisco SD-Access underlay network?

Options

• AEnd user subnets and endpoints are part of the underlay network.
• BThe underlay switches provide endpoint physical connectivity for users.
• CStatic routing is a requirement,
• DIt must support IPv4 and IPv6 underlay networks

Explanation

Cisco SD-Access Underlay Network Explanation

Option B is correct because the underlay network in SD-Access is the physical infrastructure - the switches and routers that provide the actual physical connectivity for end devices (users, servers, IoT) to connect to the network. The underlay's primary role is to transport traffic between fabric nodes, and its switches serve as the physical attachment points for endpoints.

Why the distractors are wrong:

• Option A is incorrect because end-user subnets and endpoints are part of the overlay network (the fabric), not the underlay - the underlay simply provides transport
• Option C is incorrect because SD-Access underlay typically uses dynamic routing protocols (IS-IS is the default with DNA Center LAN Automation), not static routing, making static routing the opposite of the requirement
• Option D is incorrect because the SD-Access underlay only requires IPv4 - IPv6 is supported at the overlay level, not mandated for the underlay

💡 Memory Tip: Think of the underlay as the "physical foundation" - like the concrete floor of a building. It just needs to physically hold things up (connect devices) and transport traffic, while the overlay fabric handles all the intelligent segmentation and virtualization above it.

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