Paloalto Networks SD-WAN-Engineer - Palo Alto Networks SD-WAN Engineer

Comprehensive and Detailed Explanation

Prisma SD-WAN (formerly CloudGenix) integrates with Palo Alto Networks IoT Security to provide comprehensive visibility into all devices at a branch, including those that are not directly connected to the ION device. While the ION automatically detects and classifies devices connected directly to its interfaces via traffic inspection (DPI), DHCP, and ARP analysis, gaining visibility into off-branch devices (devices connected to downstream switches or access points) requires additional discovery mechanisms that can query the network infrastructure or ingest its logs.

1. SNMP (Simple Network Management Protocol): This is the primary active discovery method for off-branch devices. The Prisma SD-WAN ION device acts as a sensor that actively polls local network switches and wireless controllers using SNMP. By querying the ARP tables and MAC address tables (Bridge MIBs) of these intermediate network devices, the ION can identify endpoints that are connected to the switch ports, even if those endpoints are not currently sending traffic through the ION. This allows the system to map the topology and discover silent or lateral-traffic-only devices.

2. Syslog: In conjunction with SNMP, the IoT Security solution can utilize Syslog messages to discover and profile devices. Network infrastructure devices (like switches and WLAN controllers) can be configured to send Syslog messages to the collection point (which enables the IoT Security service) whenever a device connects or disconnects (e.g., port up/down events, DHCP snooping logs, or 802.1x authentication logs). These logs provide real-time data about device presence and identity (MAC/IP mappings) for devices that are not directly adjacent to the ION, ensuring 100% visibility across the branch network segments. LLDP (A) and CDP (B) are typically Link Layer discovery protocols used for discovering directly connected neighbors and do not propagate beyond the immediate link, making them unsuitable for discovering devices multiple hops away or behind a switch.

Comprehensive and Detailed Explanation

Dynamic VPNs (also known as ION-to-ION or Branch-to-Branch VPNs) allow Prisma SD-WAN devices to establish direct, on-demand secure tunnels between branch sites to optimize latency for peer-to-peer traffic (e.g., VoIP calls between offices).

To enable this capability, the primary architectural requirement is the configuration of VPN Clusters.

A VPN Cluster defines a logical group of devices that are authorized to communicate with one another.

By default, or if devices are in different clusters without peering, the topology typically defaults to Hub-and-Spoke, where branches only talk to the Data Center.

When two branch ION devices are placed into the same VPN Cluster (or peered clusters), the controller shares the necessary reachability and cryptographic information between them.

Once in the same cluster, the ION devices monitor traffic. If a user at Branch A tries to contact a server at Branch B, the ION devices detect this interest. If a direct path is available (e.g., via public internet), they will dynamically negotiate a direct VPN tunnel, bypassing the Data Center hub. This offloads the hub and reduces latency. Option B is incorrect because SD-WAN eliminates manual GRE config. Option C is incorrect because dynamic VPNs are a performance feature, not just a disaster recovery feature.

Comprehensive and Detailed Explanation

The transition from "Claimed" to "Online" depends entirely on the ION device's ability to establish a secure, persistent management tunnel to the Prisma SD-WAN Controller.

Connectivity Requirements: The ION device initiates an outbound connection to the controller on TCP Port 443 (HTTPS). It also requires accurate time synchronization to validate SSL certificates, necessitating access to NTP (UDP Port 123).

Scenario Analysis: Since the installer can browse the internet from the LAN, we know the physical link and basic routing/NAT are functional. The issue is specific to the management plane traffic.

Root Cause: If an upstream firewall (e.g., a corporate edge firewall or ISP filter) is inspecting SSL traffic or blocking specific FQDNs/Ports required by the ION, the device cannot complete the handshake. Consequently, it remains "Claimed" (registered in the database) but cannot go "Online" (active management session). Options A, C, and D prevent provisioning (configuration push) but generally do not prevent the device from initially checking in and going "Online" if the pipe is open.

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 of 16 QoS queues.

This 16-queue structure is derived from a matrix of 4 Classes (often referred to as Priority Classes) multiplied by 4 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): Within each of 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 Queues per 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.

Prisma SD-WAN High Availability (HA) for branch ION devices, particularly the Gen-2 ION 1200-S, is designed to provide "100% WAN Capacity" preservation during a hardware or power failure. This is achieved through the use of Bypass Pairs (Fail-to-Wire). In the provided topology, the ISP A and LTE/5G circuits are cross-connected using the bypass ports (typically ports 3 and 4 on the ION 1200-S).

When the "Active" ION device loses power, the internal physical relays in its bypass ports transition to a closed state, effectively creating a physical bridge between the ports. In this scenario, the LTE/5G signal—which enters the Active ION's port 4—is mechanically bridged to port 3, allowing it to pass through to port 4 of the Standby ION. Simultaneously, ISP A is already connected to the Standby ION. Consequently, once the Standby device completes its transition to the "Active" state, it has physical access to both WAN circuits, validating Statement A.

Regarding the LAN transition, Prisma SD-WAN does not use standard VRRP for ION-to-ION HA; instead, it uses a proprietary Control Plane HA mechanism. When the failover occurs, the newly active ION takes over the IP addresses of all configured Switch Virtual Interfaces (SVIs) and LAN interfaces. To ensure the downstream Layer 2 infrastructure (like the LAN switches shown in the diagram) updates its MAC address tables to point to the new physical hardware for those IPs, the newly active ION immediately broadcasts a Gratuitous ARP (GARP). This ensures that LAN traffic is correctly steered to the new device without a significant timeout, validating Statement C.

Comprehensive and Detailed Explanation

In Prisma SD-WAN, Custom Applications are global policy objects managed centrally on the controller.

Immediate Propagation: When an administrator creates or modifies a Custom Application definition (e.g., updating the IP subnet or port for an internal app), the Prisma SD-WAN controller automatically pushes this update to all connected ION devices in the tenant.

No Manual Push: Unlike some legacy firewall management paradigms (like Panorama "Commit and Push"), the Prisma SD-WAN architecture is "intent-based" and continuously synchronized. A change to a global object like an App Definition is considered a live configuration change and is distributed immediately via the secure control channel.

No Reboot: The ION data plane updates its classification engine dynamically without interrupting traffic or requiring a reboot. This ensures that policy enforcement (steering "Inventory_App" to the correct path) remains accurate in real-time.

Comprehensive and Detailed Explanation

When deploying Prisma Access for Remote Networks (connecting branch offices), the licensing and throughput model is based on aggregate bandwidth allocated to specific compute locations (regions).

Bandwidth Allocation (Option D): Administrators must purchase and allocate a specific amount of bandwidth (e.g., 500 Mbps, 1 Gbps) to a Prisma Access "Compute Location" (e.g., US West, Europe Central). This allocated bandwidth is then shared as a pool among all the branch sites (Remote Networks) that onboard and terminate their IPSec tunnels at that specific location. The system does not allocate bandwidth on a strict per-site basis but rather enforces the limit on the aggregate throughput of the compute node itself.

Policy Enforcement (Option A): Security policies for Prisma Access are enforced in the cloud (at the Prisma Access Service Processing Node), not pushed down to the branch ION devices for local enforcement. The ION device handles local segmentation (ZBFW) and traffic steering, but the "Remote Network" security stack resides in the cloud.

Path Usage (Option C): Prisma SD-WAN is designed to utilize Active/Active paths. When a branch has multiple internet circuits connected to Prisma Access, the CloudBlade and ION automatically build tunnels on all compatible paths and can load-balance traffic across them based on application performance (SLA), rather than defaulting to a strict Active/Standby model for internet traffic.

Prisma SD-WAN is built on an application-defined fabric that prioritizes deep visibility into network traffic and application performance.1 To deliver the high-fidelity flow data and application visibility required for modern operations, Prisma SD-WAN utilizes IPFIX (Internet Protocol Flow Information Export).2 IPFIX is a standardized protocol based on NetFlow v9 that allows for the export of IP flow information from network devices to a collector or management system.3

In the Prisma SD-WAN architecture, ION devices act as the exporters.4 Because the system is application-aware, it doesn't just export basic 5-tuple information (source/destination IP, ports, and protocol); it exports rich metadata including application IDs, performance metrics (latency, jitter, packet loss), and path information. This allows the Prisma SD-WAN Controller and the associated Analytics engine to reconstruct a complete picture of every flow in the network.

While other protocols like SNMPv3 are supported for basic device health monitoring (such as CPU or interface status) and ADEM (Autonomous Digital Experience Management) provides end-to-end visibility for mobile users or SASE-connected branches, IPFIX is the primary "engine" for flow-level data across the SD-WAN fabric. Unlike traditional IP SLA, which relies on synthetic probes, the IPFIX-based monitoring in Prisma SD-WAN uses real-time application traffic to assess performance. This ensures that the visibility provided in the Flow Browser and Analytics dashboards accurately reflects the actual user experience, enabling granular troubleshooting and proactive capacity planning.

In Prisma SD-WAN, Performance Policies are the primary mechanism used to define the expected quality of experience for specific applications. Unlike traditional monitoring that relies solely on "up/down" interface states, Prisma SD-WAN focuses on the actual health of the application path. An incident is triggered when the system detects a violation of defined service-level agreement (SLA) thresholds, such as excessive latency, jitter, or packet loss, even if the physical link remains active.

When an administrator configures a performance policy, they set specific bounds for these metrics. For example, a VoIP application might have an SLA requiring latency below 150ms and packet loss below 1%. If the ION device detects that the current path (e.g., a broadband circuit) exceeds these limits, it generates a performance incident. This incident serves two purposes: first, it alerts the administrator to the degradation; second, it triggers the Path Selection engine to proactively steer the application traffic to a more suitable "Backup" or "Available" path that currently meets the SLA requirements.

Options B, C, and D represent system-level or network-level events that generate different types of alerts or incidents (System or Network incidents), but they are not the triggers defined within a Performance Policy. Performance policies are specifically concerned with the application's perceived performance across the fabric. By focusing on SLA violations rather than just physical link status, Prisma SD-WAN ensures that business-critical applications remain functional even during "brownout" conditions where a circuit is technically "up" but performing poorly.