Paloalto Networks Network Security Administrator SD-WAN-Engineer New Questions

Comprehensive and Detailed Explanation

Prisma SD-WAN supports Dynamic VPNs (Branch-to-Branch) even when both endpoints are behind Source NAT (e.g., typical broadband connections).

To achieve this, the ION devices utilize standard NAT Traversal techniques, specifically leveraging STUN (Session Traversal Utilities for NAT).

Discovery:Each ION communicates with the Cloud Controller (which acts as a STUN server/signaling broker). Through this communication, the controller observes thepublicIP and Port that the ION's traffic is coming from (the post-NAT address).

Signaling:The controller shares this public reachability information with the peer ION.

Hole Punching:The IONs then attempt to initiate connections to each other's discovered public IP/Port. This "UDP Hole Punching" allows them to establish a direct IPSec tunnel through the NAT devices without requiring static 1:1 NAT mapping or manual port forwarding on the provider routers, enabling mesh connectivity in commodity internet environments.

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

Prisma SD-WAN utilizes a hierarchical QoS model (typically based onHierarchical Token Bucketor similar shaping algorithms) to manage bandwidth contention.

Guaranteed Bandwidth:The "Platinum" class (used for Real-Time voice/video) is assigned aguaranteed bandwidth percentage(floor) in the QoS profile. This ensures that even if "Gold" (Transactional) or "Silver" (Bulk) traffic is trying to consume 100% of the link, the scheduler reserves the specific portion (e.g., 30%) for Platinum traffic, preventing starvation.

Shaping, not Policing:Unlike simple policing which drops excess traffic hard, the ION deviceshapesthe egress traffic. If the link is congested, the scheduler delays the lower-priority packets (buffering) to allow the high-priority Platinum packets to exit immediately.

Why not Strict Priority (A)?While Platinum behaveslikea priority queue, pure Strict Priority can completely starve lower queues if the high-priority traffic is misbehaving or voluminous. Prisma SD-WAN typically uses bandwidth guarantees (floors) and limits (ceilings) to ensure fair sharing while protecting critical apps.

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.