Cisco Updated 300-420 Exam Questions and Answers by zian

A fabric edge node in Cisco SD-Access is the access-layer fabric device that connects endpoints to the fabric, applies policy, and registers endpoint reachability with the control plane. Cisco SD-Access design material describes edge nodes as devices that identify and authenticate endpoints, place them into the correct virtual network, and update the fabric control plane with endpoint information. The edge node is also where the anycast Layer 3 gateway commonly resides, allowing consistent gateway behavior across the fabric. Option B describes the control-plane node function, because the control plane maintains endpoint-to-location mappings in the host tracking database. Option C describes a border node, which connects the fabric to external Layer 3 networks. Option D also describes the map-resolver behavior associated with the control plane, not the fabric edge. The purpose of the edge node is therefore endpoint attachment, endpoint detection, policy association, and registration of endpoint information with the control plane so the fabric can forward traffic through the correct overlay path.

An on-change telemetry subscription is the best solution when the team needs device state data while limiting impact on the device. With periodic telemetry, the device sends subscribed data at a configured interval regardless of whether the value has changed. For state such as shared memory utilization, aggressive periodic polling or streaming can create unnecessary CPU, memory, and bandwidth overhead, especially at scale. On-change telemetry sends an update only when the subscribed data changes, or when a relevant event occurs according to the model and platform behavior. This reduces needless data transmission while still providing timely visibility into meaningful state changes. IPFIX is designed for flow information and traffic accounting rather than detailed device state telemetry. Static telemetry is not the best characterization of the efficient event-driven behavior required here. A periodic subscription can provide the data, but it continuously streams updates and therefore has greater device and collector impact. Cisco model-driven telemetry design favors on-change subscriptions when the operational requirement is state awareness with minimal repeated polling.