The correct action is to configure EIGRP stub behavior on R4. The DUAL-3-SIA message indicates a Stuck-in-Active condition, which occurs when EIGRP sends a query and does not receive a reply within the expected time. Cisco explains that EIGRP stub routing is used to improve stability and reduce resource usage by preventing unnecessary queries from being sent to remote or edge routers. In the described topology, R4 is connected over a limited 10 Mbps inter-router link and should not be treated as a transit router for the rest of the routing domain. Making R4 an EIGRP stub limits the query scope and reduces the chance of active routes waiting on a slow or constrained neighbor. Poison reverse and split-horizon changes address loop prevention and hub-and-spoke update behavior, but they do not directly solve the SIA instability. A summary on R2 may help scaling but does not identify the edge-router query boundary as precisely as EIGRP stub. Reference topics: EIGRP DUAL, Stuck-in-Active, EIGRP stub routing, query scoping, WAN edge stability.

The control-plane node in Cisco SD-Access acts as the map system that manages endpoint-to-device relationships. Cisco SD-Access documentation describes control-plane nodes as maintaining the host database that maps endpoint identifiers to the fabric edge devices where those endpoints are attached. This mapping function is based on LISP control-plane behavior. When an endpoint appears on an edge node, the edge registers the endpoint information with the control plane. When another fabric device needs to send traffic to that endpoint, it queries the control-plane node to resolve the endpoint location. A fabric edge node is the device that connects wired endpoints to the fabric, so option A describes an edge role. Wireless endpoints may attach through fabric AP and fabric WLC integration, but that is not the control-plane node’s role. External Layer 3 networks are connected through border nodes, not through the control-plane node. Therefore, the correct role is endpoint-to-device mapping. Accurate control-plane design is essential for fabric scale, endpoint mobility, and fast location resolution.

As a STUN server, Cisco vBond allows Cisco Catalyst SD-WAN routers to discover their public mapped IP addresses and ports when they sit behind NAT. This function is essential during overlay bring-up because many WAN Edge devices are deployed behind internet circuits, firewalls, or provider NAT devices. vBond helps devices understand how they are seen from the public transport side and facilitates the formation of secure control connections to the SD-WAN controllers. vBond also participates in orchestration and Zero-Touch Provisioning workflows, but the question specifically asks about its purpose as a Session Traversal Utilities for NAT server. That wording points directly to NAT discovery, not general ZTP. vBond does not secure user data traffic between edge routers; data-plane encryption is established between WAN Edge devices. It also has no role in integrating SD-Access wireless into a fabric. Reference topics: Cisco SD-WAN vBond, STUN, NAT traversal, orchestration, WAN Edge onboarding. This is fundamental for internet transports.

GETVPN is the correct transport-encryption design for this environment. The company is using a private MPLS-based service and requires encryption without maintaining permanent point-to-point tunnels. GETVPN was designed for private WAN environments where routing remains native and packets are encrypted without adding GRE or IPsec tunnel overlays between every pair of sites. It uses group-based keying, typically with key servers that distribute security policy and rekey material to group members. That supports dynamic key rotation and spoke-to-spoke communication while avoiding the operational burden of building and maintaining individual tunnels. DMVPN also supports dynamic spoke-to-spoke tunnels, but it is still a tunnel overlay using mGRE, NHRP, and IPsec, and it is usually selected for Internet or mixed transport overlays. Standard IPsec VPN requires maintaining tunnel relationships, and GRE VPN alone does not provide encryption. GETVPN therefore best matches tunnel-less encryption across a private MPLS WAN with centralized security policy and direct site-to-site forwarding. Reference topics: GETVPN, group encrypted transport, tunnel-less IPsec, private MPLS WAN encryption, group keying.

Implementing network summarization on the edge routers is the correct EIGRP design action to reduce query range and improve convergence. In EIGRP, when a route is lost and no feasible successor exists, DUAL sends queries to neighbors. If the network is large or poorly summarized, those queries can propagate widely and increase convergence time. Hierarchical addressing allows each office or edge block to advertise a summary instead of many specific prefixes. If a specific subnet inside an office fails, the summary can remain stable toward the rest of the network, preventing the failure from triggering unnecessary queries across the dark-fiber interoffice topology. Stub routing can also reduce query scope, but the option says to configure stub areas on non-edge routers, which is not the right EIGRP terminology or placement. Different EIGRP processes add redistribution complexity, and route filtering alone does not provide the same clean convergence boundary as summarization. Reference topics: EIGRP summarization, DUAL query scope, hierarchical addressing, convergence optimization, dark-fiber campus routing.

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.

VRRP advertisements are sent by the current master router and include priority information used by the backup routers to evaluate mastership. In VRRP, the master is the router actively forwarding for the virtual IP address. Backups listen for advertisements; if advertisements stop, the backup with the highest effective priority can become master. This is why the statement that advertisements are sent only from the master router is correct. The advertisement also carries priority information, which is used in election behavior and failover decisions. Standby or backup routers do not normally send VRRP advertisements while a master is active, so option A is incorrect. The default advertisement interval is not three seconds in standard VRRP behavior; three seconds is commonly associated with other first-hop redundancy defaults such as HSRP hellos. Although timer fields exist in protocol operation, the exam focus here is the master-only advertisement behavior and the priority carried in those advertisements. In campus gateway redundancy design, VRRP advertisements must be protected from loss or filtering because missed advertisements can cause unnecessary master transitions.

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.

Running BFD between EIGRP neighbors is the appropriate design when the problem is traffic loss during link failure and the requirement is to reduce the impact of the failure. EIGRP can detect neighbor loss through its hello and hold timers, but those timers may not be fast enough for applications sensitive to packet loss. Bidirectional Forwarding Detection provides rapid failure detection independent of the routing protocol’s normal timer expiration. When BFD detects a failed forwarding path, it notifies EIGRP so the routing process can converge without waiting for the EIGRP hold timer. Summarization is still a valuable scaling technique, but it primarily reduces route table size and query scope; it does not directly accelerate failure detection on an individual inter-router link. Reducing EIGRP hello and hold timers can improve detection, but it increases control-plane load and is less efficient than BFD. The question emphasizes data loss when any one link fails, so fast failure detection is the best corrective design. Reference topics: EIGRP convergence, BFD, failure detection, hello and hold timers, routed-link resiliency.

The fabric control plane in Cisco SD-Access creates and resolves endpoint-to-location mappings. SD-Access separates endpoint identity from physical topology by using LISP in the control plane. Endpoint addresses are treated as Endpoint Identifiers, and fabric node locations are represented by Routing Locators. When an endpoint appears on a fabric edge node, the edge registers that endpoint-to-edge binding with the control-plane node. When another edge needs to send traffic to that endpoint, it queries the control plane to resolve the current location and then uses the fabric data plane to encapsulate traffic toward the correct destination. Group-Based Access Control policy creation and enforcement involve Cisco ISE, security group tags, and policy components rather than the basic mapping purpose of the fabric control plane. BGP route reflection is not the SD-Access control-plane function, and extending multiple subnets to one RLOC is not the main purpose. Reference topics: SD-Access control plane, LISP, EID-to-RLOC mapping, endpoint registration, map resolution.