300-420 Exam Dumps : Designing Cisco Enterprise Networks

Option B is retained because the subnetting task depends on the exhibit options and the chosen plan must divide 10.1.8.0/21 into nonoverlapping partner VPN subnets without allocating more address space than required. The design principle is variable-length subnet masking: allocate the smallest subnet that satisfies each partner requirement, then place the subnets on valid prefix boundaries inside the reserved aggregate. Cisco addressing design emphasizes conserving address space, avoiding overlap, and preserving summarization where possible. A /21 provides 2048 total addresses, so the designer can carve several smaller partner ranges while keeping the entire allocation summarizable as 10.1.8.0/21 toward the data-center core. Incorrect options would either waste addresses, overlap existing ranges, place subnets on invalid boundaries, or allocate blocks larger than necessary. Option B is the mapping that satisfies the exhibit constraints while keeping the design clean for routing, firewall policy, and VPN onboarding. Reference topics: IPv4 VLSM, subnet boundary alignment, partner VPN addressing, summarization, nonoverlapping address design.

The correct design is to deploy the application in both data centers, advertise the application prefix from DC1 as a /32, and advertise a broader /24 from DC2. This uses longest-prefix-match behavior to create deterministic primary and backup routing. Cisco routing logic prefers the most specific matching route in the routing table, regardless of administrative distance or metric comparisons among less specific covering routes. As long as the DC1 /32 is present, traffic for that exact application address follows DC1. If DC1, its edge path, or the /32 advertisement fails, the /32 is withdrawn and the remaining /24 covering route from DC2 provides backup reachability. Advertising the same prefix from both locations may result in load sharing or provider-dependent selection, which does not guarantee DC1 primary behavior. IP SLA could be used in some route-tracking designs, but the clean routing solution tested here is prefix specificity. Reference topics: longest-prefix match, BGP advertisement, active/standby data center routing, covering routes, route failover.

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.