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

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.

The correct solution is a management VRF with SSH keys for device access. A management VRF creates a separate routing and forwarding table for management traffic, keeping administrative reachability isolated from production and overlay routes. That directly satisfies the requirement that the overlay network must not cause routing issues and makes troubleshooting easier for operations teams because management reachability can be validated independently. Cisco VRF design uses separate routing tables to isolate traffic and can support overlapping addresses or independent routing policy. For secure device access, SSH with key-based authentication provides encrypted administrative sessions and stronger authentication than clear-text or password-only methods. Private VLANs and ordinary VLANs provide Layer 2 separation but do not create independent routing tables. TACACS+ and RADIUS are AAA systems; they are useful but do not define the management transport architecture. Separate physical interfaces can be useful out-of-band, but the best match for overlay isolation and operational simplicity is management VRF plus SSH keys. Reference topics: management VRF, secure device access, SSH public-key authentication, routing-table isolation, enterprise management design.

For streaming multimedia over a WAN using DiffServ per-hop behavior, the best answer is CBWFQ with DSCP AF3. Cisco QoS design separates real-time interactive voice from streaming multimedia. Voice bearer traffic commonly uses EF and a strict priority queue because it is extremely sensitive to delay and jitter. Streaming multimedia, however, is usually buffered and bandwidth-intensive; it should receive assured bandwidth and controlled drop behavior rather than strict priority treatment. The Assured Forwarding classes are designed for this kind of preferential forwarding within DiffServ. AF3 is commonly associated with multimedia streaming in Cisco QoS baseline models, while CBWFQ provides bandwidth guarantees without allowing the class to starve other traffic. LLQ with EF is too aggressive for streaming multimedia and should be reserved for voice bearer traffic or similarly strict real-time flows. AF2 is more commonly used for transactional data or lower-priority assured service, depending on the model. The correct marking and queuing design is therefore CBWFQ with DSCP AF3. Reference topics: DiffServ, per-hop behavior, CBWFQ, DSCP AF classes, multimedia streaming QoS.