Cisco Designing Cisco Enterprise Networks Exam 300-420 ENSLD Exam Questions

Answer : D

NETCONF supports XML, while RESTCONF supports both XML and JSON. Cisco programmability documentation describes NETCONF as an XML-based protocol that exchanges RPC requests and replies such as get, get-config, and edit-config using XML encoding. NETCONF is tightly aligned with YANG-modeled data, but the protocol message format itself is XML. RESTCONF exposes YANG-modeled data through an HTTP or HTTPS API and can represent payloads in XML or JSON. Cisco DevNet material commonly summarizes the comparison as NETCONF equals XML, while RESTCONF equals XML or JSON. That is why option D is accurate. Option A is wrong because NETCONF does not use JSON in the same way RESTCONF does. Option B is incomplete because RESTCONF is not limited to JSON. Option C reverses the protocol encodings. This distinction matters in automation design because tool selection, content type, parsing, and API workflows differ by protocol. Reference topics: NETCONF, RESTCONF, YANG, XML encoding, JSON encoding, model-driven programmability.

Answer : A, B

PIM-SSM with IGMPv3 is the correct multicast design. Source-Specific Multicast requires receivers to identify both the multicast group and the permitted source, normally through IGMPv3 membership reports. That source-specific join model prevents unauthorized or spoofed sources from injecting traffic into the group because receivers do not simply accept traffic from any source for a group address. It also improves bandwidth efficiency because the network builds forwarding state only for the requested source and group pair, without requiring shared trees or rendezvous point discovery. PIM-SM with MSDP can interconnect multicast domains, but it is built around Any-Source Multicast behavior and does not provide the same source-specific anti-spoofing property. IGMPv2 cannot signal source-specific joins, which is why IGMPv3 is required for SSM. Since the network may merge with another multicast domain later, SSM also reduces integration complexity by avoiding RP and MSDP dependencies. Therefore, PIM-SSM and IGMPv3 meet both the security and efficiency requirements. Reference topics: PIM-SSM, IGMPv3, source-specific joins, multicast security, bandwidth efficiency.

Answer : D

VRF-Lite with OSPF satisfies the requirements because it creates multiple isolated Layer 3 routing tables without requiring a service-provider MPLS core or specialized hardware. Each VRF has its own forwarding table, interfaces, and route exchange process, so overlapping IP address space can exist in different virtual networks. When communication between segments is required, the design can use controlled route leaking, a firewall, or a shared-services VRF. OSPF can run per VRF to exchange routes within each isolated segment using widely supported routing technology. VSS, vPC, and plain 802.1Q with HSRP can improve Layer 2 or device redundancy, but they do not provide independent Layer 3 routing tables with overlapping addressing. A multihop MPLS design can also support many VPNs, but it is more complex and beyond the stated need for widely available technologies without specialized equipment. VRF-Lite is therefore the correct enterprise campus segmentation choice. Reference topics: VRF-Lite, virtual routing and forwarding, inter-VRF routing, overlapping IP address support, campus segmentation.

Answer : B

The selected IPv4 plan is correct because the design must maximize the number of subnets while still meeting the host requirements for each location. With VLSM, the largest subnet must be allocated first. A segment requiring 500 hosts needs at least 9 host bits, because 2^9 provides 512 addresses and 510 usable host addresses, so a /23 is required. A segment requiring 100 hosts needs 7 host bits, giving 126 usable addresses, so a /25 is sufficient. A segment requiring 25 hosts needs 5 host bits, giving 30 usable addresses, so a /27 is sufficient. Any plan that uses larger prefixes than necessary wastes addresses and reduces the number of available subnets inside 172.16.0.0/16. Any plan using smaller subnets would fail the host requirement. The correct option is the one that uses the smallest valid subnet size for each requirement while keeping the addressing blocks aligned. Reference topics: IPv4 VLSM, CIDR, subnet sizing, usable host calculation, hierarchical addressing plans.

Answer : D

The requirements point to a Layer 2 multipoint WAN service. VPLS provides an emulated Ethernet LAN across a provider network, allowing multiple sites to appear as if they are connected to the same Layer 2 domain. This supports full-mesh Layer 2 connectivity and preserves customer control over higher-layer services such as IPv6, multicast, routing protocols, and QoS markings. Because the provider delivers an Ethernet multipoint service, the enterprise can retain protocol independence rather than depending on the service provider to participate in IPv6 routing or multicast routing. CoS marking is also a Layer 2 QoS mechanism, so a Layer 2 VPN service is better aligned to the stated QoS requirement. VPWS is point-to-point rather than full-mesh multipoint, so it does not meet the topology requirement by itself. MPLS Layer 3 VPN is a provider-routed service and does not give the customer full Layer 2 mesh behavior. DMVPN is an overlay routed VPN and does not provide a native Layer 2 full-mesh service. Therefore, VPLS is the correct WAN connectivity option.

Answer : B, D

The valid EIGRP stub options listed are receive-only and summary. Cisco EIGRP stub routing lets a remote or spoke router advertise only selected route types to upstream neighbors, which reduces query scope and improves stability in hub-and-spoke designs. The summary option permits the stub router to advertise summary routes. The receive-only option makes the router receive routes but not advertise routes, which is useful when the device should not be considered a transit or route source. ''External'' is also a real EIGRP stub keyword in Cisco IOS, but in this specific option set the verified pair expected by the question is receive-only and summary. ''Summary-only'' is not the correct EIGRP stub keyword. ''Totally-stubby'' and ''not-so-stubby'' are OSPF area concepts, not EIGRP stub router options. In design terms, EIGRP stub routing is used to prevent unnecessary queries from being sent toward routers that cannot provide alternate paths. This is especially important for low-resource branch routers and DMVPN spokes, where limiting control-plane workload directly improves convergence behavior.

Answer : C

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.