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

The IPv4 network 172.16.10.0/24 maps to 2001:db8:abcd::ac10:a00/120 when the IPv4 address is placed into the lowest significant bits of the IPv6 address. The calculation converts each IPv4 octet into hexadecimal: 172 is AC, 16 is 10, 10 is 0A, and 0 is 00. Combining those bytes gives AC10:0A00, displayed in IPv6 notation as ac10:a00. Because a /24 IPv4 network has 8 host bits, the mapped IPv6 network leaves the same 8 host bits, resulting in a /120 IPv6 prefix. Option B incorrectly places decimal IPv4 octets into separate IPv6 hextets and uses /96, which represents a much larger mapping block than the /24 network. Option C does not represent 172.16.10.0 in hexadecimal. Option D changes the higher-order IPv6 prefix and does not match the supplied address plan. The correct address therefore preserves the planned IPv6 prefix and embeds the IPv4 network in the low-order bits. Reference topics: IPv4-to-IPv6 address mapping, hexadecimal conversion, IPv6 prefix length, migration addressing plans.

Dual multihomed is the only listed WAN design that satisfies all failure conditions: CE, PE, ISP, and link failure. A single-homed design has one provider attachment and cannot survive most of those events. A single multihomed design uses more than one provider or provider connection, but if it still has only one customer edge device, a CE failure remains a single point of failure. A dual-homed design can provide multiple links to one provider, but it may not protect against a complete ISP failure. Dual multihoming combines redundant customer edge devices with connections to multiple provider edge devices and, typically, multiple providers. Cisco WAN and BGP design guidance uses multihoming to increase availability, control inbound and outbound path selection, and avoid dependence on a single provider path. This design gives the architect the necessary device, link, and provider diversity. Reference topics: WAN edge redundancy, BGP multihoming, dual-provider design, CE and PE resiliency, internet edge high availability.

Traffic shaping is required in the parent policy when hierarchical QoS uses CBWFQ in the child policy for low-bandwidth remote sites. In Cisco hierarchical QoS, the parent policy commonly shapes outbound traffic to the real available rate of the WAN service, especially when the physical interface speed is higher than the provider committed rate. The child policy then applies class-based queuing, such as CBWFQ and LLQ, inside the shaped rate. This structure creates an artificial congestion point on the router so the child queues can schedule packets predictably instead of allowing the provider to drop traffic after it exceeds the service rate. Policing in the child policy would drop excess packets and is not the normal prerequisite for nested CBWFQ. CBWFQ is supported in child policies within hierarchical designs, and parent shaping is the mechanism that makes the hierarchy effective. This is especially important on low-bandwidth WAN links where voice, video, and business-critical applications require deterministic treatment. Reference topics: hierarchical QoS, CBWFQ, parent shaping, child queuing, WAN QoS design.