The correct answer is C. A point-to-point Layer 3 underlay network with jumbo frames enabled .
In Cisco SD-Access , the fabric is built on top of an underlay network . Cisco documentation states that the SD-Access underlay uses a structured Layer 3 foundation and a Layer 3 routed access design , where the network elements establish IP connectivity through routing rather than relying on Layer 2 adjacency. Cisco Catalyst Center LAN automation documentation also describes the underlay links as point-to-point Layer 3 routed connections .
This makes Option C the best answer because it matches the recommended SD-Access design approach:
Routed access instead of Layer 2 campus meshing
Jumbo frames enabled to accommodate encapsulation overhead commonly associated with fabric technologies such as VXLAN in software-defined fabrics, which is a standard design consideration in Cisco fabric deployments.
Why the other options are incorrect:
A. A fully meshed Layer 2 topology This is not the SD-Access design model. Cisco SD-Access is not based on a campus-wide Layer 2 mesh; instead, it uses a routed Layer 3 underlay.
B. A fully meshed Layer 3 topology SD-Access does require Layer 3 underlay connectivity, but not a fully meshed Layer 3 topology . Cisco recommends a structured routed access design , not an every-device-to-every-device full mesh.
D. A point-to-point Layer 2 network with LACP between devices for redundancy This contradicts the SD-Access underlay principle. The underlay should be Layer 3 point-to-point , not Layer 2 point-to-point.
ENCOR exam point:
For Cisco SD-Access, remember this core design rule:
Underlay = routed, point-to-point, Layer 3 foundation
Overlay = virtualized fabric services on top of that underlay
