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

Forward error correction and quality of service are the two listed techniques that directly improve application experience in a Cisco SD-WAN design. Forward error correction protects selected application traffic by sending recovery information so packet loss can be corrected without waiting for retransmission. That is especially useful for real-time voice and video traffic, where retransmission delay can degrade quality. QoS improves application treatment by classifying, marking, queuing, shaping, and prioritizing traffic according to business intent and application sensitivity. Cisco SD-WAN designs commonly combine application-aware routing, QoS, and loss-mitigation features to keep critical traffic on the best path and preserve service quality during congestion or impairment. A stateful firewall, AMP, and Cisco Umbrella improve security posture, but they do not primarily improve application experience in the forwarding-quality sense asked by the question. They may protect applications, but they do not directly address loss, delay, jitter, and congestion treatment. Therefore, FEC and QoS are the best answers. Reference topics: Cisco SD-WAN application experience, FEC, QoS, loss mitigation, real-time traffic handling.

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.

When Cisco SD-WAN edge router redundancy is designed, VRRP is the supported first-hop redundancy protocol in the SD-WAN edge context. VRRP provides a virtual default gateway for LAN-side devices, allowing one WAN Edge router to act as the active gateway while another can take over if the active router or tracked condition fails. Cisco SD-WAN designs use VRRP with tracking and policy alignment so branch LAN traffic can fail over to the appropriate edge router while the SD-WAN overlay handles transport and tunnel selection. HSRP and GLBP are traditional campus first-hop redundancy protocols, but they are not the supported FHRP answer for vEdge router redundancy in this design context. OMP is the SD-WAN control-plane routing protocol used between WAN Edge routers and vSmart controllers; it is not a first-hop redundancy protocol for LAN hosts. Therefore, the correct FHRP for vEdge router redundancy is VRRP. The design should also ensure that VRRP priorities, tracking, and SD-WAN routing preferences align so traffic exits the intended edge during normal and failure conditions.