NSE4 High Availability and Diagnostics Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  diagnose sys session filter src 10.0.1.10 ; diagnose sys session list

  Why it's wrong here

  The command pair `diagnose sys session filter src 10.0.1.10 ; diagnose sys session list` queries the session table and prints a point-in-time snapshot of active sessions that match the source IP filter. It does not provide real-time tracing of packet processing through the kernel, nor does it show debug messages as packets traverse firewall policies, session creation, or routing lookups. The `diagnose sys session` utility is for inspecting established session entries, not for streaming per-packet debug flow events, so it cannot reveal transient drops or policy decisions.

• ✓

  diagnose debug flow filter src 10.0.1.10 ; diagnose debug flow show function-name ; diagnose debug enable

  Why this is correct

  This correct sequence first installs a flow trace filter for the source IP, then selects the `function-name` output mode to display the names of kernel functions that process the matching packets, and finally enables debug output. The order is critical because the filter must be active before debugging starts to avoid capturing unrelated traffic, and the `show` option must be set before `enable` takes effect. Once enabled, the FortiGate outputs a step-by-step traversal of the packet through the firewall, including policy lookups, session setup, and any drops, which is exactly what real-time debugging requires.

• ✗

  diagnose sniffer packet any 'host 10.0.1.10' 4

  Why it's wrong here

  The command `diagnose sniffer packet any 'host 10.0.1.10' 4` runs a packet sniffer on all interfaces with a host filter and a verbosity level of 4 (typically full header and payload display). While it captures raw frames in real time and can show the packet contents, it operates at a different layer: it shows the actual packets on the wire but does not expose the internal software path or the firewall's decision-making process. The sniffer cannot show which policy matched, whether a session was denied, or why a packet was dropped, so it is unsuitable for flow debugging compared to `diagnose debug flow`.

• ✗

  diagnose debug reset ; diagnose debug enable ; diagnose debug flow show iprope

  Why it's wrong here

  This attempt is invalid because the debug enable is executed before the flow filter and output options are configured, so the debugger would start with default settings and no source IP filter, generating a flood of output for all flows. Additionally, `diagnose debug flow show iprope` is placed after `diagnose debug enable`, meaning the output format selection is ineffective; in the proper sequence, filter and show commands must precede `diagnose debug enable`. The `diagnose debug reset` only clears previous settings and does not set a filter, and the absence of a `filter` command means the administrator cannot narrow the trace to the host 10.0.1.10, making the output unmanageable and incomplete.

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