300-420 Exam Dumps : Designing Cisco Enterprise Networks

Route summarization should be planned from the aggregation layer toward both the core and the access layer. In hierarchical campus routing, aggregation or distribution devices are natural summarization boundaries because they sit between more specific access-layer networks and the core. Summarizing from aggregation toward the core prevents access-layer subnet churn from forcing unnecessary recomputation and route table growth in the core. Summarizing from aggregation toward access can also provide a concise upstream route, often a default or summary route, so access devices do not need the entire network routing table. The goal is to contain failures, reduce routing state, and preserve fast convergence at hierarchy boundaries. Summarizing from the core toward aggregation may hide useful topology details in the wrong direction, while summarizing directly from access toward aggregation is not always possible or efficient when access devices are numerous and have limited resources. The answer that places summarization at aggregation in both directions best matches Cisco hierarchical design principles. Reference topics: hierarchical campus design, route summarization, aggregation layer, core route scale, convergence containment.

In Cisco SD-Access, an intermediate node is an underlay transit device. Its responsibility is to provide IP reachability between fabric edge nodes, border nodes, and other fabric infrastructure roles. Intermediate nodes forward routed underlay traffic and do not perform endpoint registration, endpoint lookup, or VXLAN encapsulation for user traffic. Endpoint-to-location mapping is handled through the fabric control plane, which is based on LISP map-server and map-resolver functions. Fabric edge nodes identify connected endpoints, apply policy, act as anycast gateways, and encapsulate user traffic into VXLAN. Border nodes connect the fabric to external networks and handle traffic entering or leaving the fabric. The intermediate node is therefore comparable to a routed distribution or core transport device in a traditional hierarchical campus, except it is participating in the SD-Access underlay. It must provide stable Layer 3 reachability and appropriate MTU for encapsulated traffic but does not maintain the host tracking database or add security group information to VXLAN headers. The correct function is transporting IP packets between edge and border nodes.

The correct design is to use the same anycast RP address on loopback interfaces so receivers and sources register with their nearest available rendezvous point. Cisco Anycast RP designs use a common RP address advertised from multiple RP routers, allowing unicast routing to direct PIM joins and registers to the closest RP. MSDP is then used between the RP routers so each RP can learn about active sources registered to the other RP. This provides resilience and local registration while keeping RP reachability consistent for the multicast domain. Option B captures the key behavior: the RP loopback is configured with the same /32 address, and normal routing sends traffic to the closest RP. Configuring a hash value, group range splitting, or equal priority alone does not provide the Anycast RP behavior required here. A professional design should also use unique loopbacks for MSDP peer sessions while keeping the shared anycast loopback as the RP address. Reference topics: Anycast RP, MSDP, PIM-SM rendezvous points, source registration, multicast high availability.