Paloalto Networks Updated SD-WAN-Engineer Exam Questions and Answers by renzo

Comprehensive and Detailed Explanation

The Prisma SD-WAN (ION) QoS engine utilizes a hierarchical queuing structure designed to provide granular control over application performance. Each WAN interface on an ION device supports a total of16 QoS queues.

This 16-queue structure is derived from a matrix of4 Classes(often referred to as Priority Classes) multiplied by4 Application Criteria(Traffic Types).2

4 Priority Classes:The system defines four high-level business priority categories:3

Platinum(Highest priority)4

Gold

Silver

Bronze(Lowest priority/Best Effort)5

4 Application Criteria (Sub-queues):Withineachof the four priority classes, the system further categorizes traffic into four specific application types to ensure proper handling (e.g., ensuring voice doesn't get stuck behind bulk data even within the same priority level):6

Real-Time Video

Real-Time Audio

Transactional

Bulk7

Calculation:4 Priority Classes × 4 Application Types =16 Total Queuesper interface. This structure allows the scheduler to ensure that a "Platinum" voice call is prioritized over "Platinum" bulk data, and both are prioritized over "Gold" traffic.

Comprehensive and Detailed Explanation

In Prisma SD-WAN, security policies can be applied viaPolicy Stacks, which often have a hierarchy.

Stack Precedence:A common configuration involves aGlobal Security Stack(applied to all sites) and aLocal/Site Security Stack(specific to one site). If the administrator configured a "Global" rule that says "Deny Access to Gambling Sites" (or a specific IP list), and that rule is higher in the binding order or part of a higher-priority stack, it will enforce the blockbeforethe local "Allow Guest to Internet" rule is processed.

Specifics of "REJECT":The state REJECT specifically implies a policy enforcement action (sending a TCP RST or ICMP Unreachable) rather than a silent drop or a routing failure.

Why not A?If the "Allow" rule is at the top and matches the traffic parameters (Zone/IP), the Default Deny at the bottom would never be reached. The issue implies ahigher priorityDeny exists.

Comprehensive and Detailed Explanation

Prisma SD-WAN calculates the Mean Opinion Score (MOS) to provide a standardized metric (1-5) for voice quality. To ensure the system always knows the "voice readiness" of a path—even before a call starts—it uses Active Probes (synthetic UDP packets).

While latency is measured, the MOS calculation algorithm is most heavily penalized by Packet Loss (D) and Jitter (B).

Packet Loss:Even a small amount of loss (e.g., >1%) dramatically reduces voice clarity, causing dropouts.

Jitter: High variance in packet arrival time (jitter) causes the "robotic" voice effect and buffer underruns.

The system continuously measures these specific metrics on all WAN links using synthetic probes. If the packet loss or jitter exceeds the threshold defined in the "Path Quality Profile" (e.g., Voice Profile), the path is marked as non-compliant, and the MOS score drops, triggering a policy action to move the flow. Throughput (C) is less critical for voice as calls consume very little bandwidth (e.g., 64-100 Kbps), making congestion (loss/jitter) the primary enemy, not raw speed.

Comprehensive and Detailed Explanation

The CLI command debug controller reachability (e.g., debug controller reachability 1) is the specific diagnostic tool designed to verify the entire connectivity chain required for management plane availability.

Unlike a simple ICMP ping (Option A), which only tests Layer 3 connectivity to an IP address, the debug controller reachability command performs a sequential set of tests:

DNS Resolution:It attempts to resolve the specificLocatorservice URL (locator.cgnx.net or region-specific FQDN) to verify DNS functionality.

TCP Connectivity:It tests the ability to establish a TCP connection to the controller on port 443 (HTTPS).

SSL/TLS Handshake: It validates that the device can successfully negotiate the secure tunnel required for authentication.

If this command fails at the DNS step, the issue is likely a missing DNS server in the interface config. If it fails at the TCP step, it implies an upstream firewall is blocking outbound port 443. This targeted output allows the engineer to pinpoint exactly why the device is offline in the portal.