CCNP Enterprise 300-420 Release Date

Dual stack is the correct migration strategy when the application chooses IPv6 or IPv4 based on DNS resolution. In a dual-stack deployment, hosts and network devices run IPv4 and IPv6 at the same time. Applications can query DNS and then select the protocol based on the returned records, such as using an AAAA record for IPv6 or an A record for IPv4. This gives the organization a controlled migration path because IPv6-capable applications and services can move to IPv6 while legacy IPv4 services remain reachable during the transition. Address-family translation for public web presence is useful when IPv6-only and IPv4-only endpoints must communicate through a translation boundary, but it does not provide native application choice between the protocols. Host-initiated tunnels and site-to-site IPv6-over-IPv4 tunnels encapsulate one protocol over another and add operational overhead. The question’s key phrase is that the application chooses between IPv6 and IPv4 based on DNS; that is the normal dual-stack behavior. Reference topics: IPv6 migration, dual stack, DNS A and AAAA records, transition strategy, application protocol selection.

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 best answer is to use a single IP address for a static NAT entry that represents the server with a nonoverlapping address. When two companies use overlapping private address space, routing directly between the networks can fail because each side may already have a local route for the same prefix. The requirement is narrow: users in the acquired company need access to one server in Company A, and the design must conserve address space. A static NAT mapping for the server solves the destination overlap problem with one translated address, giving remote users a unique reachable address for that server without renumbering either company. Overload NAT is normally used to translate many inside clients behind one address for outbound access; it is not the most precise solution for publishing one overlapping server. One-to-one NAT for every user wastes addresses and adds operational overhead. Readdressing the acquired company would solve the overlap permanently, but it does not conserve effort or address space. Therefore, a single static NAT entry for the server is the most efficient design.

The border node is part of the Cisco SD-Access overlay architecture. In the SD-Access fabric, the overlay consists of fabric roles and services that provide endpoint connectivity, segmentation, policy, and external reachability over the routed underlay. Border nodes connect the fabric overlay to external Layer 3 networks, shared services, WAN, Internet, or other fabric/transit domains. They perform the fabric boundary function, including routing between virtual networks and external routing domains as designed. Spine and leaf are generic data center or fabric topology terms and are not the named SD-Access fabric overlay roles in this question. Cisco DNA Center, now Cisco Catalyst Center, is central to management, automation, assurance, and policy deployment, but it is not itself an overlay forwarding component. The forwarding overlay is built from roles such as edge, border, control-plane, and intermediate nodes. Therefore, the correct component from the options is the border node. The design should select border placement based on external connectivity, scale, route control, redundancy, and whether the border is internal, external, or anywhere border. Reference topics: SD-Access overlay, border node, fabric roles, external connectivity, virtual networks.