Cisco Updated 300-420 Exam Questions and Answers by ignacy

The drag-and-drop mapping identifies which elements belong to each model-driven protocol or data-modeling mechanism. Cisco programmability designs distinguish the data model, the encoding, and the transport protocol. YANG defines the structure of configuration and operational data. NETCONF commonly uses XML encoding and provides transactional operations such as get-config, edit-config, lock, and commit-like workflow depending on platform support. RESTCONF exposes YANG-modeled data through HTTP methods and typically uses URI-based resources with XML or JSON encoding. gRPC and gNMI are commonly used for efficient telemetry or operational data streaming, with protocol buffers often used for serialization. The selected mapping follows those protocol boundaries rather than mixing model structure with transport behavior. In design work, this matters because the same network feature can be represented by a YANG model but accessed through different protocols, each with different capabilities, security requirements, and operational semantics. Correctly matching elements to protocols avoids invalid payloads and broken automation workflows. Reference topics: YANG, NETCONF, RESTCONF, gRPC, gNMI, XML and JSON encoding, model-driven telemetry.

Both WAN routers should run OSPFv2. The requirement explicitly says that the routing protocol must be open standard, provide high availability, and offer fast convergence. OSPF is an open-standard link-state routing protocol and is broadly supported across vendors. It builds a link-state database, calculates best paths with SPF, supports equal-cost multipath, and can be tuned with BFD, SPF throttling, LSA throttling, and hierarchical areas for resilient enterprise WAN designs. EIGRP is fast and operationally efficient in Cisco-only environments, but it is not the best answer when the requirement emphasizes an open-standard routing protocol. Running OSPFv2 on one router and OSPFv3 on another is invalid for a single IPv4 routing design because they would not form the intended common routing domain. Mixing IS-IS and OSPFv3 also fails the requirement for a unified design between the redundant routers. Therefore, both routers should run OSPFv2. Reference topics: OSPFv2, open-standard routing, WAN routing high availability, link-state convergence, ECMP and BFD integration.

NETCONF: SSH-based; built to support candidate configuration. RESTCONF: HTTPS-based; lacks support for two-phase commit transactions.

NETCONF and RESTCONF both use YANG data models, but they use different transport and transaction behaviors. NETCONF is traditionally SSH-based and was designed as a network configuration protocol with datastore concepts such as running, startup, and candidate configuration where supported. The candidate datastore enables staged configuration changes and a commit workflow, which is useful for transactional network changes. RESTCONF exposes YANG-modeled resources through an HTTP-based REST interface, typically protected with HTTPS. It is simpler for web-style application integration because it uses familiar HTTP methods, URIs, and payload encodings such as XML or JSON. However, RESTCONF does not provide the same full two-phase commit transaction model associated with NETCONF candidate configuration workflows. Therefore, the correct mapping is that NETCONF is SSH-based and built to support candidate configuration, while RESTCONF is HTTPS-based and lacks support for two-phase commit transactions. In Cisco programmability design, NETCONF is often selected for robust configuration transactions, whereas RESTCONF is often selected for simpler API-driven integration.

GRE over IPsec is the correct secure tunneling choice when multicast traffic must cross a public network. Native IPsec protects unicast IP traffic, but it does not inherently carry multicast routing protocols or multicast application flows in the same way that GRE can. GRE creates a logical point-to-point tunnel that can encapsulate multicast, broadcast, and non-IP payloads; IPsec then encrypts the GRE packet for confidentiality and integrity across the untrusted transport. Cisco designs commonly use this combination when dynamic routing protocols, multicast applications, or other non-unicast traffic must be transported securely between sites. GRE by itself supports multicast, but it does not provide encryption, so it fails the secure tunneling requirement. PPTP is obsolete and not appropriate for modern enterprise design. Plain IPsec is secure, but it is not the complete answer when multicast support is explicitly required. Therefore, the design should use GRE over IPsec: GRE supplies the multicast-capable overlay, and IPsec supplies the cryptographic protection across the public network.