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

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.

Bidirectional PIM is the correct multicast protocol for this many-to-many financial application. The question states that most multicast sources also receive multicast traffic and that the design must not use source trees. Cisco describes BIDIR-PIM as a multicast mode built for many-to-many applications that use a shared tree rooted at the rendezvous point and avoid per-source shortest-path trees. This reduces multicast state because routers do not maintain separate source/group state for every active sender. PIM Sparse Mode can start with a shared tree, but it can switch to source trees, which violates the stated requirement. PIM-SSM is explicitly source-specific and requires receiver knowledge of the source, so it is not appropriate for a many-to-many model where source trees are disallowed. MSDP is not a multicast forwarding mode; it is used for source discovery between PIM-SM domains. The option text contains a spelling error, but the intended answer is BIDIR-PIM. The architect should verify RP placement, Designated Forwarder behavior, group ranges, and whether the application can tolerate shared-tree forwarding rather than shortest-path source trees. Reference topics: BIDIR-PIM, many-to-many multicast, shared tree, source-tree avoidance, multicast scaling.

The SD-Access overlay should reduce subnet sprawl and avoid overlapping IP subnets unless there is a specific operational requirement. Cisco SD-Access creates overlay virtual networks over an IP underlay and uses anycast gateway, VXLAN encapsulation, LISP control-plane mapping, and policy constructs to simplify endpoint mobility and segmentation. Reducing the number of subnets simplifies DHCP scope management, default-gateway placement, and operational troubleshooting. Avoiding overlapping address space across overlay networks is also a practical design recommendation because overlapping subnets complicate shared services, fusion routing, security logging, and policy troubleshooting. LAN automation and a dedicated IGP process are underlay deployment considerations, not overlay design choices. Layer 3 to the access design is also associated with routed underlay and campus fabric transport, not the overlay segmentation model. A clean overlay design should define virtual networks, scalable groups, IP pools, shared-services reachability, and external connectivity before deployment. Reference topics: Cisco SD-Access overlay design, anycast gateway, virtual networks, DHCP simplification, overlapping subnet avoidance.