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 multicast Reverse Path Forwarding check is a loop-prevention mechanism. Cisco multicast forwarding does not forward traffic merely because the packet arrived on any multicast-enabled interface. Instead, the router checks whether the packet arrived on the interface that would be used to route traffic back toward the multicast source or, in shared-tree cases, back toward the rendezvous point. If the packet arrives on the expected reverse path, it passes the RPF check and can be replicated to the outgoing interface list. If it arrives on the wrong interface, it is dropped to prevent loops and duplicate packets. This supports a loop-free multicast distribution tree from sources to receivers. Auto-RP mapping agents, bootstrap messages, and RP-set discovery are separate rendezvous point distribution mechanisms; they are not the function of the RPF check. In enterprise designs with redundant links, asymmetric routing, or multiple equal paths, multicast RPF behavior must be reviewed carefully because unicast routing choices directly influence whether multicast packets are accepted or discarded. Reference topics: multicast RPF, PIM forwarding, loop prevention, outgoing interface list.

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.