300-420 Exam Dumps : Designing Cisco Enterprise Networks (ENSLD) v1.1

The selected configuration sets are correct because the addressing plan must use VLSM to maximize subnets and minimize wasted addresses. Customer A requires 125 hosts, so it needs a /25 subnet, which provides 126 usable host addresses. Customer D requires 62 hosts, so it needs a /26 subnet, which provides 62 usable addresses exactly. Point-to-point or small WAN links B, C, and E should use the smallest appropriate link subnets shown in the exhibit, typically /30 for IPv4 point-to-point links when two usable addresses are required. A correct plan must allocate the largest blocks first, align every subnet on the proper boundary, avoid overlap, and avoid assigning a larger-than-needed subnet to any customer or link. Options A and C are the two valid combinations that satisfy those rules in the exhibit. Any option that places a /25 or /26 on the wrong boundary, overlaps with another block, or wastes larger subnets on links would fail the design objective. Reference topics: IPv4 VLSM, subnet boundary alignment, host capacity planning, point-to-point addressing, route summarization readiness.

The correct overlay considerations are that virtual networks provide data-plane isolation and that overlapping IP addresses should be avoided for operational simplicity. In Cisco SD-Access, virtual networks are used for macro segmentation and are commonly mapped to VRFs. This separates routing and forwarding tables between major groups such as corporate users, guests, IoT, and shared services. Security Group Tags provide finer policy control and microsegmentation, but they are not the primary mechanism for data-plane isolation between virtual networks. The phrase “virtual networks should be used for microsegmentation” is therefore inaccurate; microsegmentation is SGT and SGACL driven. Although overlapping IP addresses can technically exist in separate VRF-like contexts, Cisco design practice discourages unnecessary overlap because it complicates troubleshooting, service insertion, external connectivity, and inter-VN communication. A clean overlay address plan improves operations and reduces policy ambiguity. Reference topics: SD-Access overlay design, virtual networks, macro segmentation, SGTs, microsegmentation, overlapping IP avoidance. This also simplifies day-two operations.

The branch subnets must each support up to 200 hosts, so /120 is the correct IPv6 prefix length from the available options. A /120 provides 256 IPv6 addresses, which satisfies the 200-host requirement. A /121 provides only 128 addresses, which is not enough. The parent block is 2a01:0c30:0016:7009::3800/118. A /118 has 10 host bits, so it contains 1024 addresses and spans from ::3800 through ::3bff. The valid /120 boundaries inside that parent are ::3800/120, ::3900/120, ::3a00/120, and ::3b00/120. From the listed choices, 2a01:0c30:0016:7009::3a00/120 and 2a01:0c30:0016:7009::3b00/120 both fall inside the parent allocation and provide enough address capacity. The /121 options are too small, and ::3c00/120 is outside the /118 parent range. This is a straightforward IPv6 prefix-boundary and capacity calculation. Reference topics: IPv6 subnetting, prefix length, address block boundaries, branch address planning.