300-420 Exam Dumps : Designing Cisco Enterprise Networks (ENSLD) v1.1

The selected design is correct because the requirement describes a resilient campus architecture that must support the same VXLAN at any access-layer switch while maintaining fast convergence and high availability. In Cisco campus and data-center-style fabric designs, VXLAN provides network virtualization by carrying Layer 2 adjacency over a routed or resilient transport. The correct design must avoid a fragile single spanning-tree domain and must provide redundant forwarding paths so that an access switch or uplink failure does not isolate the VLAN or VXLAN segment. The selected option represents the design that meets those conditions by allowing the overlay segment to be extended consistently across access switches while keeping the underlay resilient. Designs that rely on a traditional Layer 2 tree, a single aggregation point, or blocked redundant links would not meet the high availability and fast convergence objectives. The important design principle is that VXLAN should ride on a stable, redundant transport and should not depend on large Layer 2 failure domains. Reference topics: VXLAN campus design, overlay networking, fast convergence, access-layer resiliency, high availability.

An inbound IP prefix list is the correct tool because the routers must decide which prefixes to accept from the service provider based only on prefix length. Prefix lists are designed to match network prefixes and mask-length ranges using operators such as le and ge. Applying the prefix list inbound to the BGP neighbors prevents routes with masks longer than /24 from entering the local BGP table, regardless of what the service provider advertises. This conserves memory and ensures the customer routing policy is enforced locally. An access list is a poor fit because it does not natively express prefix-length logic as cleanly as a prefix list. Applying the policy outbound would filter routes the customer sends to the provider, which is the wrong direction; the requirement is about routes the customer learns. A route map could reference a prefix list, but the simplest and most exact answer is to use an IP prefix list inbound. Therefore, the design should apply an inbound prefix list to both BGP peers to block prefixes greater than /24. Reference topics: BGP route filtering, prefix lists, inbound policy, maximum accepted prefix length.

The SD-Access control-plane node performs the LISP Map-Server and Map-Resolver functions. Cisco SD-Access uses LISP in the control plane to maintain mappings between endpoint identifiers and routing locators. Fabric edge nodes discover local endpoints and register them with the control-plane node. When a destination endpoint is not known locally, a fabric node queries the control-plane node, which resolves the endpoint location and returns the locator information needed for VXLAN forwarding through the fabric. This is why the control-plane node is the correct answer. A fabric edge node connects endpoints, provides the anycast gateway, encapsulates and decapsulates user traffic, and registers endpoints. A border node connects the fabric to external networks. An intermediate node simply transports routed underlay traffic between fabric nodes and does not hold endpoint mappings. In design terms, control-plane placement and redundancy are critical because endpoint mobility, fabric forwarding lookup, and location resolution depend on stable Map-Server and Map-Resolver services. Reference topics: Cisco SD-Access control plane, LISP Map-Server, LISP Map-Resolver, EID-to-RLOC mapping, fabric edge registration.