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

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.

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 specific Locator service 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.

Comprehensive and Detailed Explanation

In a Prisma SD-WAN Data Center deployment, the operational state of the Secure Fabric VPNs (overlay tunnels) is directly tied to the health of the BGP Core Peer configuration.4

Core Peer Dependency: DC ION devices typically peer with the data center core switch (Core Router) via BGP to learn the subnets (prefixes) for the applications hosted in the DC. The Prisma SD-WAN controller monitors this BGP peering status.5

Controller Logic: If the BGP Core Peer on a DC ION goes down (or is not established), the controller automatically marks the VPN tunnels terminating at that specific ION as "Inactive".6 This is a fail-safe mechanism designed to prevent remote branches from sending traffic to a DC ION that has lost conne7ctivity to the internal data center network (and thus the applications).

Scenario Analysis: In this scenario, DC ION-1 has active VPNs, meaning its BGP Core Peer is UP and it is successfully advertising reachability. DC ION-2 has no active VPNs, which strongly indicates that its BGP Core Peer is down.8 Because the controller sees the peer is down, it suppresses the tunnel establishment or marks existing tunnels as inactive to ensure traffic is only directed to the healthy node (ION-1).

In Prisma SD-WAN, application performance is monitored through distinct metrics that separate network health from application health. The provided graph displays Network Transfer Time (NTT) in blue and Server Response Time (SRT) in orange. NTT measures the round-trip time of packets traversing the WAN fabric, while SRT measures the time elapsed from when the server receives a request to when it sends the first response packet.

Analysis of the telemetry data shows that the NTT (blue line) remains consistently low and stable, generally staying below 100 milliseconds throughout the capture period. This indicates that the SD-WAN path and underlying network circuits are not the source of the latency. Conversely, the SRT (orange line) exhibits significant and erratic spikes, reaching as high as 450 to 475 milliseconds. These spikes occur while the network latency (NTT) remains flat.

Because the latency increases are isolated to the SRT metric, the root cause is confirmed to be on the Application Server side. This pattern typically suggests that the server is struggling with resource exhaustion, high CPU utilization, or database query delays during peak processing times. For a real-time application, these SRT spikes translate directly to jitter and "lag" for the end-user. By distinguishing between these two metrics, Prisma SD-WAN allows network administrators to prove that the network is performing within SLA and shift the troubleshooting focus to the application or server management teams, significantly reducing mean time to innocence (MTTI).