300-420 Exam Dumps : Designing Cisco Enterprise Networks

The Cisco SD-Access data plane is based on VXLAN. Cisco SD-Access separates the fabric into functional planes: the underlay provides IP reachability, the control plane uses LISP to map endpoints to locations, and the data plane uses VXLAN encapsulation to carry user traffic across the routed underlay. VXLAN allows the fabric edge node to encapsulate endpoint traffic and forward it through the fabric while preserving virtual network and segmentation information. This is what enables SD-Access to provide Layer 2 and Layer 3 overlay services over a Layer 3 routed transport. OMP is the control-plane protocol for Cisco SD-WAN, not SD-Access. NHRP is associated with DMVPN tunnel resolution. LISP is essential in SD-Access, but its role is endpoint ID to routing locator mapping, not packet encapsulation in the data plane. Therefore, VXLAN is the correct protocol for the SD-Access data plane. Reference topics: SD-Access fabric, VXLAN data plane, LISP control plane, overlay encapsulation, routed underlay.

Route summarization and EIGRP stub routing are the two correct design techniques for a stable and scalable EIGRP deployment. Summarization reduces the number of prefixes advertised upstream, conserves bandwidth and memory, hides route flaps behind the summary boundary, and reduces the size of the EIGRP topology table. Stub routing prevents branch or access devices from being used as transit routers and limits the scope of EIGRP queries. This is critical because uncontrolled EIGRP query propagation can increase convergence time and processing load, especially in larger hierarchical networks. Prefix lists and distribute lists can filter routes, but filtering alone does not provide the same query-boundary and topology-hiding benefits as summarization and stubs. Static redistribution increases complexity and can create loop or policy risks if not controlled with tags and metrics. The question specifically asks to conserve bandwidth, memory, and CPU, prevent suboptimal routing, and avoid unnecessary queries; summarization and stub routing are the direct Cisco design answers. The architect should summarize at hierarchy boundaries and configure access or branch routers as EIGRP stubs where they should not provide transit. Reference topics: EIGRP summarization, EIGRP stub routing, query scope, hierarchical routing.

The design must enable IPv6 multi-topology behavior at the appropriate edge routers and move metric handling toward transition support where the current IS-IS network still uses narrow metrics. Multi-topology IS-IS is important during IPv4-to-IPv6 migration because IPv4 and IPv6 reachability do not always exist on identical links at every stage of the migration. If IPv6 follows the IPv4 topology when some devices or paths are not IPv6-ready, traffic can be blackholed. Multi-topology allows independent IPv4 and IPv6 SPF calculations, which prevents IPv6 traffic from being forwarded through IPv4-only portions of the network. The metric-style transition setting is used when migrating from narrow to wide metrics, allowing interoperability while routers are upgraded and the design scales. Because the requirement says IPv6 areas will grow and the current network uses narrow metrics, the selected edge devices must support the IPv6 topology and metric transition behavior shown in the exhibit. Reference topics: IS-IS IPv6, multi-topology IS-IS, narrow metrics, wide metric transition, IPv6 migration, blackhole prevention.