Score Higher on Verified SD-WAN-Engineer | Palo Alto Networks SD-WAN Engineer Exam Questions with Answers

Comprehensive and Detailed Explanation

Prisma SD-WAN utilizes Link Quality Monitoring (LQM) to maintain a real-time health score for every WAN path.

To ensure the system knows the quality of a path before sending critical user traffic onto it, the ION device uses Active Probing.

Mechanism: The ION sends synthetic probe packets (typically UDP) across the Secure Fabric (VPN tunnels) and Direct Internet paths to its peers. These probes measure Latency, Jitter, and Packet Loss.

Active vs. Passive: While the system does use Passive Monitoring (observing actual user flows) when traffic is present to reduce overhead, Active Probes are essential for idle links or backup paths. Without active probing, the ION would have no data to make an intelligent steering decision for the first packet of a new video call. This ensures that "Real-Time" policies always have up-to-date metrics to select the best path immediately.

Comprehensive and Detailed Explanation

Prisma Access manages Remote Network bandwidth using an Aggregate Bandwidth licensing model.

Compute Locations: When you purchase bandwidth (e.g., 1 Gbps), you allocate it to specific Prisma Access Compute Locations (e.g., US West, Europe Central).

Shared Pool: All branch sites (Remote Networks) that connect to that specific Compute Location share the allocated bandwidth pool. For example, if you allocate 500 Mbps to "US West" and connect 10 branches to it, they compete for that 500 Mbps aggregate.

Bursting: An individual branch is not strictly rate-limited to a "slice" (e.g., 50 Mbps) unless you explicitly configure QoS guarantees. By default, a single branch can burst and consume a large portion of the aggregate pool if other branches are idle. The enforcement happens at the Region/Compute Node level, ensuring the total throughput does not exceed the licensed capacity for that region.

Comprehensive and Detailed Explanation

The Bypass Pair feature on Prisma SD-WAN ION devices (specifically supported models like ION 2000, 3000, 7000, 9000) is a hardware-based resiliency mechanism known as Fail-to-Wire.

Operation: A "Bypass Pair" logically groups two physical interfaces (e.g., WAN 1 and LAN 1). Under normal operation, the ION processes traffic between them.

Power Loss: In the event of a total power loss (or critical software failure), a mechanical relay inside the device physically closes the circuit between the two ports.

Result: This creates a direct electrical connection (like a patch cable) between the upstream device (ISP Modem) and the downstream device (Legacy Firewall or Router). This ensures that internet connectivity is preserved for the site, even if the SD-WAN appliance is completely dead. This is critical for single-point-of-failure deployments where maintaining basic dial-tone is more important than SD-WAN optimization during a hardware outage.