SD-WAN-Engineer Exam Dumps - Palo Alto Networks SD-WAN Engineer

Comprehensive and Detailed Explanation

Prisma SD-WAN utilizes STUN (Session Traversal Utilities for NAT) to facilitate NAT Traversal for its Secure Fabric overlay.

Discovery: When an ION device connects to the internet behind a NAT router, it reaches out to the Prisma SD-WAN Controller. The controller acts as a STUN server, identifying the public IP address and port that the ION's traffic is originating from.

Symmetric NAT Challenge: In Symmetric NAT, the mapping changes for every destination. However, the Prisma SD-WAN architecture is designed to handle this by having the controller coordinate the connection attempt.

Hole Punching: The controller shares the discovered public mapping information between two peer ION devices. They then simultaneously initiate traffic to each other's public IP/Port (a technique called "UDP Hole Punching"). This tricks the intermediate NAT devices into allowing the inbound traffic, establishing a direct P2P IPSec tunnel without requiring manual port forwarding or static IPs at the edge.

Comprehensive and Detailed Explanation

The SITE_CONNECTIVITY_DOWN alarm is a high-severity alert indicating a total loss of overlay connectivity for a site.

It does not trigger if just one circuit fails (Option B), provided that other circuits are still up and maintaining VPNs. A single link failure would typically trigger a "Link Down" or "VPN Down" alarm, but the Site connectivity would remain "Up" (degraded).

It does not simply mean the device rebooted (Option A), although a reboot would cause it temporarily; the alarm specifically tracks the state of the VPN fabric.

The SITE_CONNECTIVITY_DOWN alarm specifically generates when all Secure Fabric Links (VPN tunnels) on the device are in the "Down" state. This means the branch is completely isolated from the rest of the SD-WAN network (Data Centers and other branches), even if the device itself might still be powered on and reachable via the controller (management plane). It signifies a "Blackout" of the data plane for that location.

Comprehensive and Detailed Explanation

In the Prisma Access architecture (integrated with SD-WAN), distinct connection types serve different purposes.

Remote Networks: These are the connections from your Branch sites (using ION devices) into the cloud. They allow branches to get to the internet or other branches.

Service Connections (SC): This is a specialized high-bandwidth connection used to bridge the Prisma Access Cloud to your Private Data Center or Headquarters.

The primary use case for a Service Connection (Option A) is to allow mobile users and branch users (who are connected to the Prisma cloud) to reach private, centralized resources that still reside on-premise, such as Active Directory controllers, legacy databases, or mainframes. Without a Service Connection, users in the cloud would be able to reach the internet and each other, but not the servers physically located in your HQ data center. The CloudBlade automates the creation of these tunnels, but architecturally, the "Service Connection" is the "cloud-to-HQ" bridge.

Comprehensive and Detailed Explanation

In the Prisma SD-WAN architecture, the terminology distinguishes between "Native" automation and "Legacy" interoperability.

Secure Fabric Links: These are the proprietary, automated overlay tunnels created between two Prisma SD-WAN ION devices (e.g., Branch ION to Data Center ION). The controller automatically manages the IP addressing, key rotation, and routing for these links. You do not manually configure "Phase 1" or "Phase 2" parameters for Secure Fabric links.

Standard VPNs: These are traditional, standards-based IPSec tunnels configured to connect an ION device to a Non-ION endpoint (Third-Party Peer). This is used for "Data Center to Data Center" connections where one side is a legacy firewall (e.g., Cisco ASA, Palo Alto Networks NGFW) or for connecting to cloud security services (SSE) that do not have a specific CloudBlade integration. For a Standard VPN, the administrator must manually define the IKE/IPSec profiles, pre-shared keys, and peer IP addresses to match the third-party device's configuration.

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.

In Prisma SD-WAN, the Signal-to-Noise Ratio (SNR) is a critical metric used to monitor the health and performance of cellular WAN interfaces. SNR measures the strength of the desired signal relative to the background noise level; higher values indicate a cleaner signal, while lower values suggest that noise is overwhelming the signal, typically leading to increased packet loss, high latency, and reduced throughput.

Analyzing the provided graph, Carrier-1 (blue line) shows a severe drop in SNR, plummeting from approximately 4.5 dB to nearly 0.3 dB between 15:00 and 23:00. An SNR value this low is indicative of a failing or highly unstable link that cannot reliably sustain data traffic, directly supporting Inference A—that Carrier-1 experienced significant performance degradation. In contrast, Carrier-2 (green line) maintains a much higher and more consistent SNR throughout the same period.

Prisma SD-WAN’s AppFabric uses application-based path selection and SLA monitoring to ensure the best possible user experience. When the system detects that a primary path (like Carrier-1) has degraded below acceptable thresholds—often triggered by high loss or latency resulting from poor signal quality—it will dynamically steer application flows to an alternative healthy path. Therefore, Inference D is correct: because Carrier-1’s quality became untenable while Carrier-2 remained stable, the ION device would have likely initiated a path switchover to move traffic from the degraded Carrier-1 to the healthier Carrier-2.

Comprehensive and Detailed Explanation

To diagnose specific VPN negotiation failures (Phase 1 or Phase 2 IPSec issues), the Event Logs (specifically filtered for System or VPN events) are the correct resource.

Event Logs: This section records the control plane signaling messages. If a VPN tunnel fails to establish, the Event Log will generate an entry containing the specific IKE failure reason sent by the peer or generated locally. Common errors found here include INVALID_COOKIE, NO_PROPOSAL_CHOSEN (mismatch in encryption algorithms), or PRE_SHARED_KEY_MISMATCH.

Flow Browser (A): This shows user traffic (TCP/UDP sessions). If the VPN is down, user traffic won't even enter the tunnel, so the Flow Browser will just show dropped flows or blackholes, but it won't explain why the tunnel itself is broken.

Link Quality (D): This shows latency/loss graphs for established tunnels. It cannot diagnose why a tunnel failed to form in the first place.

In the Prisma SD-WAN ecosystem, the centralized cloud controller provides a robust multi-layered visibility framework to ensure network reliability. To effectively detect critical events like site outages or application performance issues (SLA violations), the controller aggregates several types of operational data. Incidents are the primary mechanism for high-level alerting; they are automatically generated when the system detects significant state changes, such as an ION device going offline (site outage) or a path failing to meet the required performance metrics.

While Incidents provide the "what" and "where," Alerts offer granular notifications for specific events that may not yet have escalated to a full-scale incident. To provide deep context, the controller also utilizes Statistics, which include real-time and historical telemetry regarding bandwidth, latency, jitter, and packet loss. These statistics allow administrators to visualize the specific SLA violation as it occurs. Furthermore, Audit logs are essential for tracking configuration changes or administrative actions that might have preceded an outage, helping engineers correlate human intervention with network behavior.

By combining these four elements—Incidents for major events, Alerts for specific notifications, Statistics for performance validation, and Audit logs for change tracking—a network administrator gains a 360-degree view of the fabric. This comprehensive approach moves beyond simple "up/down" monitoring, allowing for "Day 2" operational excellence where performance degradation is identified and remediated before it impacts the end-user experience.