Free Cisco 300-420 Practice Exam with Questions & Answers | Set: 5

A scalable two-level IS-IS design uses Level 1 areas for internal campus routing and Level 2 for the interarea backbone. Each campus should have a unique IS-IS NET area value so the internal routers belong to that campus’s Level 1 area. Internal campus routers should be configured as Level 1 routers, which keeps detailed campus prefixes inside the local area and prevents unnecessary propagation of more-specific routes to other campuses. At the edge of each campus, routers that connect the campus to the backbone should operate as Level 1/Level 2 routers. These routers connect the local Level 1 area to the Level 2 backbone and can summarize or control routing information between levels. IS-IS does not use BDR routers; that is an OSPF term, so option A is invalid. Assigning the same NET value everywhere collapses the hierarchy and defeats the segregation goal. MTU differences are not a hierarchy or route-segmentation tool. Therefore, the design should use unique NET values per campus with Level 1 internal routers and Level 1/Level 2 routers at the campus edge.

OpenConfig separates intended configuration from operational state by using separate config and state containers, while many IETF and Cisco native models use a single hierarchy for configuration and operational data or expose operational data differently. This distinction is important in automation because the client must know whether it is writing desired configuration or reading actual device state. OpenConfig’s structure was designed to provide consistent multivendor modeling, with configuration data placed under config containers and observed state under state containers. Cisco native models tend to mirror the Cisco device CLI and feature hierarchy more closely, while IETF models focus on standards-based interoperability. Option B correctly states the contrast presented in the question. Option A reverses the relationship. Option C incorrectly assigns split containers to IETF and native models. Option D incorrectly isolates Cisco native models as the only split-container style. Reference topics: YANG model structure, OpenConfig config and state containers, IETF YANG, Cisco native models, network automation data modeling.

The validated answer is Option D because this item depends on the exhibit containing configuration or model fragments. In Cisco programmability questions, the correct option is determined by whether the selected YANG or API payload accurately represents the intended configuration hierarchy, data types, and device-specific path. The answer must match the complete model structure, not merely contain the right-looking address, interface name, or protocol value. Option D should therefore be retained as the verified selection because it is the only option that aligns with the expected data model structure shown in the exhibit. For these items, the professional review must avoid inventing a replacement payload when the answer choices are embedded as images. The proper explanation is that YANG-based configuration validation requires the namespace, container path, list keys, and leaf values to match the model used by the target platform. Reference topics: YANG configuration validation, RESTCONF or NETCONF payload structure, model hierarchy, Cisco IOS XE programmability, exhibit-based option verification.

A single VPLS instance is the correct Layer 2 VPN design because the customer requires service-provider transparency and direct communication between CE routers attached to the same VLAN. Virtual Private LAN Service provides a multipoint Ethernet LAN service across a provider MPLS or IP backbone. To the customer, the provider network behaves like a transparent Layer 2 switching domain, allowing CE devices in the same VLAN to communicate directly at Layer 2. VPWS is point-to-point, so multiple VPWS circuits would be required to approximate multipoint connectivity, and the design would not provide the same transparent shared LAN behavior. Multiple VPLS instances are unnecessary when the requirement is a single VLAN or single broadcast domain. VPLS also hides provider devices from the customer Layer 2 service view while allowing MAC learning and forwarding across the provider edge. Reference topics: VPLS, Layer 2 VPN, multipoint Ethernet service, CE transparency, VLAN extension, service provider WAN design.

DMVPN is the correct overlay VPN solution for dynamic, secure, scalable branch-to-branch communication. Cisco Dynamic Multipoint VPN uses multipoint GRE, NHRP, and IPsec to support dynamic tunnel creation without manually defining a static tunnel between every branch pair. That design is well suited to a global organization where branches communicate frequently and more branches will be added later. DMVPN allows spokes to register with hubs and, depending on the phase design, establish dynamic spoke-to-spoke tunnels for direct traffic while maintaining encrypted protection with IPsec. EasyVPN is more oriented to remote-access or simplified client/server VPN deployments and is not the scalable branch mesh solution described. GETVPN is strong for private WAN encryption but does not build dynamic IPsec tunnels over an overlay in the same manner and assumes a trusted private routing core. L2TP is not the correct enterprise dynamic branch overlay. The architect should choose DMVPN and select the appropriate phase, routing protocol, summarization strategy, and IPsec profile based on branch scale and resource limits. Reference topics: DMVPN, NHRP, mGRE, IPsec protection, spoke-to-spoke dynamic tunnels.

An end-to-end QoS strategy with an SLA is the best fit for an application that cannot tolerate drops and requires very low latency across countries. The customer is asking for guaranteed service behavior, not just local classification on one router. A service line with an SLA defines the expected treatment across the provider network, including bandwidth, delay, jitter, and loss commitments. This is especially important for industrial or manufacturing applications that process large data chunks and are sensitive to packet loss. A purely domain-based PHB design can mark and forward traffic differently at each hop, but it does not by itself guarantee the business outcome unless backed by an end-to-end service agreement. A flow-based approach with per-flow queuing on every ISP node would consume more provider resources and scale poorly. FEC can help selected traffic but does not replace a QoS service model. Reference topics: QoS design, service-level agreements, end-to-end QoS, low-latency applications, loss-sensitive traffic, provider WAN services.

The correct XML/YANG data model set is the option that accurately represents the IOS XE interface hierarchy, assigns the IPv4 address to GigabitEthernet2/1/0, and uses the correct prefix length of 27. In model-driven programmability, the payload must match both the selected YANG model schema and the target platform’s interface naming conventions. For IOS XE native models, interface configuration is structured under the Cisco native namespace, with interface type and name represented in the schema before IPv4 address elements are applied. The address 10.10.10.10/27 must also support a directly connected host at 10.10.10.1/27, which places both addresses in the same 10.10.10.0/27 subnet. Options that place the address under the wrong interface type, use the wrong namespace, incorrectly represent the mask, or configure the host route rather than the interface are invalid. Option D is the only answer aligned to the IOS XE YANG structure and the requested addressing. Reference topics: IOS XE native YANG, NETCONF XML payloads, interface configuration, IPv4 prefix length, model-driven programmability.

In a Cisco SD-Access fabric, DHCP relay design must account for the fact that endpoints can attach to different fabric edge nodes while using consistent anycast gateway behavior. DHCP Option 82 is important because it inserts relay-agent information that allows the DHCP infrastructure to identify where the DHCP request originated. This enables the correct address scope and policy context to be selected for the endpoint even when the gateway address is anycast across multiple fabric edges. Cisco SD-Access DHCP guidance emphasizes the use of relay information so centralized DHCP services can assign the correct address based on fabric location and endpoint context. DHCP relay is not simply enabled on border nodes, and subnets should not be stretched across fabric edges by placing DHCP servers on borders. DHCP servers do not require a special proprietary SD-Access extension in the sense described by the incorrect option; they use standard relay information such as Option 82. Therefore, the key design consideration is enabling DHCP Option 82 so the circuit information maps the request to the fabric node where it originated.

The design must influence how EIGRP-learned routes are injected into the OSPF domain, so R2 should redistribute EIGRP into OSPF as metric-type E1 and R3 as metric-type E2. Cisco OSPF documentation distinguishes external Type 1 and Type 2 routes. An E1 route includes the external cost plus the internal OSPF cost to reach the ASBR, while an E2 route uses only the external metric. Cisco path selection prefers O E1 over O E2 for the same external destination. Therefore, making R2 advertise the EIGRP routes as E1 causes OSPF routers to prefer R2 as the exit toward the EIGRP domain. Option C adjusts OSPF-to-EIGRP redistribution, which is the wrong direction for traffic passing toward EIGRP from OSPF. Removing redistribution on R3 would reduce redundancy. Option D reverses the preference and would favor R3. Reference topics: OSPF external route types, EIGRP-to-OSPF redistribution, ASBR preference, E1 versus E2 metrics.

An out-of-band management network should be isolated from the production data network and protected with strict access control. Cisco SAFE design principles treat the management plane as a sensitive function because it provides administrative access to infrastructure devices. Isolation ensures that production outages, routing problems, or compromised user segments do not automatically remove the operator’s ability to manage routers, switches, firewalls, and controllers. Access control ensures that only authorized administrators and management systems can reach the management interfaces and protocols. The management network should not be treated as a backup data path, because that undermines separation and can expose management devices to production traffic risks. It should also not be used as a general-purpose data backup network. “Facilitate network integration” is too vague and can conflict with the isolation requirement. Therefore, the best practices are to enforce access control and ensure network isolation. In a mature design, this normally includes dedicated management interfaces or VRFs, jump hosts, AAA, logging, and tightly controlled management protocol access.