The session output includes the flags:
state=redir local may_dirty ...
npu_state=00000000
offload=0/0
The 7.6 study guide explains these flags directly:
local = "Session is to/from local stack"
redir = "Session is being processed by an application layer proxy"
may_dirty = "Session is allowed by a firewall policy"
This makes C correct, because the local flag means the session either originates from FortiGate or terminates on FortiGate. The FortiOS administration guide states the same meaning: "Session is originated from or destined for local stack." This also makes A correct. The redir flag means the session is handled by an application-layer proxy. FortiOS documents explain that proxy-based inspection buffers traffic on the FortiGate and inspects it there, and that proxy-based processing is CPU and memory-intensive Since the session also shows no NPU offload (npu_state=00000000, offload=0/0), this traffic is being handled in software/CPU, not by the NPU.
Why the other options are wrong:
B is wrong because the redir flag proves the session is not passing without inspection; it is being processed by an application-layer proxy D is wrong because there is no authentication flag in this session. In Fortinet examples of captive portal/authentication-related sessions, the session state includes auth or authed flags. The study guide shows: "Any session for traffic coming from an authenticated user contains the authed flag." This exhibit does not show auth or authed, so there is no basis to conclude the client was redirected to a captive portal for authentication.

Comprehensive and Detailed Explanation From Exact Extract of Network Security Support Engineer Study Guide (FortiOS 7.6) topics:
The correct answers are A and B . Security Fabric communication uses Fortinet-proprietary protocols, mainly FortiTelemetry and Neighbor Discovery . The study guide states that FortiTelemetry uses TCP port 8013
, and that the connection is always established by the downstream FortiGate toward the upstream FortiGate
. This validates option A . The same section also states that FortiTelemetry must be manually enabled .
More precisely, the upstream FortiGate interface must have Security Fabric Connection enabled under administrative access so it can accept incoming Security Fabric connection requests. This validates option B .
Option C is wrong because only the FortiTelemetry TCP port 8013 can be changed; Neighbor Discovery uses UDP port 8014 and cannot be changed. Option D is also wrong because Security Fabric communication is not enabled automatically among all Fortinet devices. It requires the correct Security Fabric settings, interface administrative access, and downstream authorization. The study guide's troubleshooting section confirms that when FortiTelemetry is disabled, the upstream FortiGate receives TCP 8013 SYN packets but does not complete the Security Fabric connection.

When the FortiGate enters Conserve Mode due to high memory pressure (specifically reaching the Extreme Threshold at 95% memory usage, or the Red Threshold for proxy traffic), the system prioritizes stability and preventing a system crash (kernel panic).
D). FortiGate begins dropping all new sessions to protect resources:
In Extreme Conserve Mode (95%), the FortiGate kernel acts to preserve the remaining memory for system- critical tasks (like admin access and basic packet forwarding of existing sessions). To achieve this, it drops all new session initiation requests regardless of the inspection type.
In Red Conserve Mode (88%), it specifically drops new sessions that require proxy-based inspection (as these consume the most memory), while often still allowing flow-based traffic.
Among the provided choices, "dropping new sessions" is the only standard protective mechanism FortiOS employs to stop memory usage from climbing further.
Why other options are incorrect:
A: FortiGate does not automatically reboot in conserve mode; it attempts to recover by restricting traffic.
(Reboot is a last-resort crash, not a configured action).
B: Inspection modes (Proxy vs. Flow) are defined in firewall policies and cannot be dynamically switched by the system during runtime.
C: The system does not arbitrarily stop "non-essential processes" like logging or AV. Logging is critical for audit trails. While av-failopen can be configured to bypass scanning, the system typically defaults to "Fail- Close" (dropping traffic) rather than stopping the engines themselves.
Reference:
FortiGate Security 7.6 Study Guide (Diagnostics & Resource Usage): "When memory usage reaches the extreme threshold (95%), all new sessions are dropped to prevent memory exhaustion."