300-420 Exam Dumps : Designing Cisco Enterprise Networks

For streaming multimedia over a WAN using DiffServ per-hop behavior, the best answer is CBWFQ with DSCP AF3. Cisco QoS design separates real-time interactive voice from streaming multimedia. Voice bearer traffic commonly uses EF and a strict priority queue because it is extremely sensitive to delay and jitter. Streaming multimedia, however, is usually buffered and bandwidth-intensive; it should receive assured bandwidth and controlled drop behavior rather than strict priority treatment. The Assured Forwarding classes are designed for this kind of preferential forwarding within DiffServ. AF3 is commonly associated with multimedia streaming in Cisco QoS baseline models, while CBWFQ provides bandwidth guarantees without allowing the class to starve other traffic. LLQ with EF is too aggressive for streaming multimedia and should be reserved for voice bearer traffic or similarly strict real-time flows. AF2 is more commonly used for transactional data or lower-priority assured service, depending on the model. The correct marking and queuing design is therefore CBWFQ with DSCP AF3. Reference topics: DiffServ, per-hop behavior, CBWFQ, DSCP AF classes, multimedia streaming QoS.

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.

Route summarization and EIGRP stub routing are the two correct design techniques for a stable and scalable EIGRP deployment. Summarization reduces the number of prefixes advertised upstream, conserves bandwidth and memory, hides route flaps behind the summary boundary, and reduces the size of the EIGRP topology table. Stub routing prevents branch or access devices from being used as transit routers and limits the scope of EIGRP queries. This is critical because uncontrolled EIGRP query propagation can increase convergence time and processing load, especially in larger hierarchical networks. Prefix lists and distribute lists can filter routes, but filtering alone does not provide the same query-boundary and topology-hiding benefits as summarization and stubs. Static redistribution increases complexity and can create loop or policy risks if not controlled with tags and metrics. The question specifically asks to conserve bandwidth, memory, and CPU, prevent suboptimal routing, and avoid unnecessary queries; summarization and stub routing are the direct Cisco design answers. The architect should summarize at hierarchy boundaries and configure access or branch routers as EIGRP stubs where they should not provide transit. Reference topics: EIGRP summarization, EIGRP stub routing, query scope, hierarchical routing.