Cisco Updated 300-420 Exam Questions and Answers by hassan

The design should summarize routes from the distribution layer toward the core and configure access-layer switches as EIGRP stubs. EIGRP query scope is a major design consideration in large routed campus networks. When a route is lost, EIGRP may send queries to neighbors to find an alternate path. If the network is not bounded properly, these queries can spread widely, slow convergence, and create stuck-in-active risk. Configuring the access layer as EIGRP stub tells upstream routers that the access device is not a transit path to other networks, so unnecessary queries are not sent into the access layer. Summarizing at the distribution layer toward the core hides access-link instability and provides a smaller, more stable routing table to the rest of the network. Summarizing at the access layer is usually less useful when many VLANs are aggregated at distribution. Configuring the core as stub is inappropriate because the core should provide transit. Reference topics: EIGRP stub, route summarization, query boundary, campus hierarchy, DUAL convergence.

In Cisco SD-Access, endpoints inside the fabric reach external resources through fabric border nodes. The fabric overlay uses virtual networks that map to VRFs, and the border node provides the boundary between the SD-Access fabric and external Layer 3 networks, shared services, WAN, data center, or Internet connectivity. When traffic sourced inside the fabric is destined outside the fabric, the border node de-encapsulates VXLAN traffic and forwards it into the appropriate external routing domain. The answer choice stating that fabric borders use VRFs to map VNs to VRFs best captures that design function. A fusion router can be used for inter-VN communication or shared services, but it is not how every endpoint exits the fabric. SD-Access transit links are used to connect fabric sites or carry encapsulated traffic between fabrics, not simply to reach ordinary external resources. A fabric edge encapsulates and de-encapsulates traffic for locally attached endpoints, but the fabric border is the role that connects the fabric to outside networks. Therefore, fabric border nodes are the correct design component for external resource access.

Universal PoE is the appropriate power technology when endpoint requirements vary from 30 watts up to 60 watts. Cisco Universal Power over Ethernet extends the PoE+ model and can source up to 60 watts per port by using all four cable pairs. PoE Plus supports up to 30 watts and therefore does not satisfy the upper range in the requirement. Fast PoE is concerned with how quickly power is restored during switch startup, not the maximum supported wattage. Perpetual PoE is the feature that maintains power during a switch reload, but by itself it does not define the 60-watt power class. In a complete campus design, the architect should select UPOE-capable Catalyst access switches and enable perpetual PoE behavior on ports where endpoints must remain powered during reload events. Among the answer choices, Universal PoE is the required power delivery solution because the 30-to-60 watt budget is mandatory. Reference topics: Cisco UPOE, PoE Plus, Perpetual PoE, Fast PoE, Catalyst access-layer power design.

The primary HSRP device should use the preempt delay feature. When a failed primary distribution switch returns, HSRP preemption allows it to reclaim the active gateway role because it has the higher priority. However, routing protocols, trunks, line cards, FIB programming, or upstream convergence may not be fully ready at the instant HSRP becomes active again. If the device preempts too quickly, hosts forward traffic to a gateway that is not yet ready to forward all flows, causing temporary packet loss. Cisco HSRP preempt delay prevents immediate takeover by delaying preemption after reload or interface recovery, giving the switch time to rebuild control-plane and forwarding-plane state. Increasing hello timers slows failure detection and does not solve the premature takeover problem. Applying preempt delay to the backup device is not the issue because the returning primary is the device that reclaims active state. MAC refresh timers are not the primary mechanism for this condition. Therefore, the design should configure preempt delay on the primary HSRP device. Reference topics: HSRP preemption, preempt delay, gateway recovery, campus high availability, convergence coordination.