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.

In a Data Center (DC) deployment, the ION device typically peers with a core router via Border Gateway Protocol (BGP) to exchange reachability information between the SD-WAN fabric and the legacy corporate network.2 When the ION is configured to learn only a default route ($0.0.0.0/0$) from the core, the entire SD-WAN fabric relies on this single BGP-learned route to reach internal resources not directly connected to the ION.

The primary risk in this design is network isolation caused by a BGP misconfiguration or a "soft failure" on the core router. If the BGP session stays "Up" but the core router stops advertising the default route due to a configuration error, the ION device will remove the route from its routing table. Without a valid path to the core, the branch sites connected to the DC ION will lose connectivity to all data center resources.

To mitigate this, the recommended best practice is to add a static default route with a higher Administrative Distance (AD) pointing to the core peer IPs.3 This acts as a "floating static route." Under normal operations, the BGP-learned default route (typically with an AD of 20 for eBGP) remains active in the routing table. If the BGP advertisement fails, the static route with the higher AD (e.g., 250) becomes active. This ensures that the ION device maintains a persistent gateway toward the core infrastructure, preventing total fabric isolation and providing a fail-safe mechanism while the BGP peering issue is remediated. While BFD (Option A) helps with fast peer failure detection, it does not solve the issue of a missing prefix advertisement. Static route redundancy provides the necessary architectural "safety net" for the data center's reachability.

In the Prisma SD-WAN architecture, security is built directly into the AppFabric using a centralized, controller-led approach to key management. Unlike traditional VPNs that rely on manual Internet Key Exchange (IKE) or static Pre-Shared Keys (PSKs) which can be administratively burdensome and security-vulnerable, Prisma SD-WAN automates the entire lifecycle of encrypted tunnels. The Prisma SD-WAN Controller acts as the central authority for identity and key distribution for all ION (Instant-On Network) devices within the tenant's fabric.

Specifically, the VPN shared secrets used to secure these tunnels are ephemeral and are valid for exactly 24 hours. This 24-hour validity period is a security best practice implemented by Palo Alto Networks to limit the "blast radius" or window of exposure in the unlikely event that a key is compromised. The controller automatically handles the generation, distribution, and rotation of these secrets. Before the 24-hour timer expires, the controller pushes new keys to the ION devices, which then perform a hitless rollover. This ensures that the data plane remains active and encrypted without requiring manual intervention from a network administrator. If an ION device loses its control plane connection to the controller, it will maintain its existing tunnels using the current keys until they expire, at which point it must re-authenticate with the controller to receive a new set of valid secrets. This automated rotation is a core component of the Prisma SD-WAN Zero-Trust security model.

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

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

Stack Precedence: A common configuration involves a Global Security Stack (applied to all sites) and a Local/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 block before the 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 a higher priority Deny exists.

Comprehensive and Detailed Explanation

This behavior describes the "Best Available Path" logic inherent in Prisma SD-WAN's availability design.

SLA Thresholds: Path Quality Profiles act as filters to identify compliant paths.

Total Violation: If all configured "Active" paths violate the SLA (e.g., Path A has 2% loss, Path B has 5% loss, and the threshold is 1%), the system does not drop the traffic (Option A) because maintaining connectivity is prioritized over perfect quality.

Selection Logic: The system enters a fallback state where it compares the available active paths and selects the "Least Bad" one—the path that is closest to meeting the SLA (in this case, Path A with 2% loss).

Backup Paths: Traffic would only move to a Backup path (Option D) if the policy explicitly configures the backup path to engage upon SLA violation of the active set. However, strictly speaking, if only active paths are considered and all fail, it picks the best of the active group rather than blackholing the traffic.

Comprehensive and Detailed Explanation

To validate specific packet-level details like DSCP (Differentiated Services Code Point) values, header checksums, or exact payload sizes, a Packet Capture (PCAP) is required.

PCAP Tool: Prisma SD-WAN provides a built-in PCAP utility accessible directly from the portal. The engineer can select the specific Interface (e.g., Internet 1), apply a Filter (e.g., port 5060 or host 1.2.3.4), and capture the traffic.

Analysis: The resulting .pcap file can be downloaded and opened in Wireshark. This allows the engineer to definitively see if the packets leaving the ION have DSCP EF (46) and if the packets arriving (if capturing on the other side) still retain that marking, or if the ISP has bleached it to CS0 (0).

Flow Browser (A): While it shows "Application" and metrics, the Flow Browser typically displays the assigned priority class, not necessarily the raw bit-level DSCP value present in the packet header on the wire.