300-420 Exam Dumps : Designing Cisco Enterprise Networks

The SD-WAN onboarding sequence follows the controller trust and overlay-establishment workflow. A WAN Edge device first obtains basic reachability information through manual bootstrap, ZTP, or PnP-style provisioning so it can reach the orchestration components. It then establishes secure control connectivity to the orchestrator and validates identity through the certificate and authorized serial number information. After orchestration, the device forms the required secure control connections to the management and control-plane components, receives its configuration, and participates in OMP route exchange. Finally, the WAN Edge builds encrypted data-plane tunnels to other WAN Edge devices based on the TLOC and policy information learned through the control plane. This order matters because the device cannot exchange overlay routes or build data-plane IPsec tunnels until it is authenticated and authorized in the SD-WAN fabric. Cisco SD-WAN designs rely on this sequence to support zero-touch deployment, centralized policy, and secure fabric admission. Reference topics: Cisco SD-WAN onboarding, vBond orchestration, certificate validation, OMP, TLOC exchange, data-plane tunnel establishment.

The correct design is to advertise a default route from the aggregation layer toward the access layer and summarize the VLAN subnets at the aggregation layer toward the core. Cisco hierarchical campus design places summarization at aggregation or distribution boundaries because that is where access-layer routes are collected before entering the core. Summarizing the VLAN ranges into 10.0.0.0/16 hides individual access VLAN instability from the core, reducing routing table entries, protocol churn, and memory consumption on core devices. Sending a default route from aggregation to access also keeps access switches simple and prevents them from carrying unnecessary campus routing detail. This design contains failures and convergence events inside the appropriate block. Summarizing at the access layer is less practical when multiple VLANs aggregate at distribution. Advertising a default toward the core is backwards, because the core must know the summarized access block. Reference topics: hierarchical campus routing, aggregation-layer summarization, default routing to access, route-table reduction, convergence containment.

R3 must be made an L1/L2 router so that it can connect the Level 1 area to the Level 2 backbone. IS-IS uses a two-level hierarchy. Level 1 routers know the topology inside their local area, Level 2 routers form the backbone between areas, and Level 1/Level 2 routers provide the boundary between the two. A proper IS-IS backbone cannot have isolated Level 1-only routers positioned between L1/L2 routers that need to exchange interarea reachability. If the link failure exposed an area-continuity problem, converting R3 to L1/L2 gives the area an appropriate attachment point to the backbone and restores interarea forwarding behavior. Making an unrelated router Level 1 or Level 2 only would not necessarily create the required boundary function. Simply making Area 0 L2-only is also not the focused fix if the topology still lacks a correct L1/L2 transition point. The design principle is straightforward: every Level 1 area must have a dependable L1/L2 router through which traffic can reach destinations outside the area. Reference topics: IS-IS Level 1, Level 2 backbone, L1/L2 routers, interarea reachability, hierarchical IGP design.