300-420 Exam Dumps : Designing Cisco Enterprise Networks

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.

An MPLS WAN from two separate ISPs is the strongest fit when the enterprise requires an active/backup WAN design with guaranteed SLAs for applications on either connection. MPLS VPN services are typically delivered with provider-backed service-level commitments for latency, jitter, packet loss, and availability, which is why they are selected for predictable enterprise application transport. Using two separate MPLS providers improves resiliency against a provider failure while preserving SLA-backed behavior on the backup path. A hybrid MPLS and Internet VPN model can be cost effective, but the Internet path generally does not provide the same deterministic SLA unless enhanced by a specific managed service contract. Internet from two providers improves reachability diversity but does not inherently guarantee application SLA. A single ISP hybrid design creates a provider dependency and weakens availability. Therefore, dual-provider MPLS is the conservative design for guaranteed active/backup WAN service. Reference topics: MPLS WAN design, service-level agreements, active/backup WAN, provider diversity, application performance assurance.

The correct design is to advertise a default route from the aggregation layer toward the access layer and summarize the VLAN subnets at the aggregation layer toward the core. Cisco hierarchical campus design places summarization at aggregation or distribution boundaries because that is where access-layer routes are collected before entering the core. Summarizing the VLAN ranges into 10.0.0.0/16 hides individual access VLAN instability from the core, reducing routing table entries, protocol churn, and memory consumption on core devices. Sending a default route from aggregation to access also keeps access switches simple and prevents them from carrying unnecessary campus routing detail. This design contains failures and convergence events inside the appropriate block. Summarizing at the access layer is less practical when multiple VLANs aggregate at distribution. Advertising a default toward the core is backwards, because the core must know the summarized access block. Reference topics: hierarchical campus routing, aggregation-layer summarization, default routing to access, route-table reduction, convergence containment.