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

BFD is the correct design feature for detecting a link failure within 200 ms or less without materially increasing OSPF control-plane load. Cisco uses Bidirectional Forwarding Detection as a fast, lightweight failure-detection protocol that can be associated with routing protocols such as OSPF. Instead of relying on aggressive OSPF hello and dead timers, BFD performs rapid forwarding-path checks and notifies OSPF when the path fails. This allows fast convergence while avoiding the additional routing-protocol overhead and instability that can come from very low hello timers. UDLD detects unidirectional Layer 2 fiber failures, but it is not the routing adjacency failure-detection mechanism requested here. Carrier delay can adjust interface state transition timing, but it does not provide a routing-protocol independent liveness session. Fast hellos can reduce detection time, but they increase protocol traffic and can affect overall performance. BFD is therefore the proper design choice for fast and efficient OSPF convergence. Reference topics: BFD, OSPF convergence, fast failure detection, routed campus resiliency, control-plane efficiency.

Cisco SD-WAN components map to distinct control, management, orchestration, and forwarding roles. vManage is the centralized management plane used for configuration templates, monitoring, software management, and operational visibility. vSmart is the centralized control-plane component that distributes OMP routes, TLOC information, security parameters, and centralized policy to WAN Edge devices. vBond is the orchestration component used during onboarding; it authenticates devices, helps them discover controllers, and assists with NAT traversal. The WAN Edge router, whether physical or virtual, forms the data plane at the branch, campus, or data center and forwards user traffic through secure overlay tunnels. Correctly identifying these roles is essential because SD-WAN scale and resiliency depend on separating management, control, orchestration, and forwarding responsibilities. A design that confuses vManage with vSmart or vBond will misplace policy, onboarding, and forwarding functions. Reference topics: Cisco SD-WAN architecture, vManage, vSmart, vBond, WAN Edge, OMP, overlay control plane.

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.