FCSS_NST_SE-7.6 Exam Dumps - Fortinet NSE 6 - Network Security 7.6 Support Engineer

To solve this high CPU usage scenario involving the ipsengine, we must understand the specific functions of the diagnose test application ipsmonitor commands shown in the troubleshooting steps.

Analyze the Situation:

Exhibit: The diagnose sys top output shows the ipsengine process is in a run state (R) consuming 99% CPU.

Previous Action: The administrator already ran diagnose test application ipsmonitor 5.

Result: The CPU usage did not drop.

Understand the Commands:

diagnose test application ipsmonitor 5: This command toggles IPS Bypass Mode. When enabled, the IPS engine lets traffic pass through without inspection.

Implication: If the CPU was high due to traffic volume, enabling bypass would drop the CPU load immediately.

Failure: Since the CPU remained at 99% after bypass, the ipsengine process is likely frozen, stuck, or in an internal infinite loop unrelated to the current traffic flow. The process itself is the problem, not the traffic volume.

Evaluate the Solution (Option B):

diagnose test application ipsmonitor 2: This command toggles the IPS engine's Enable/Disable status.

Because the engine is stuck (bypass failed to relieve pressure), the "Immediate action" required is to stop or restart the process entirely.

Running option 2 effectively disables/kills the stuck IPS engine instance, which will immediately drop the CPU usage to near zero. (It can then be toggled again to restart it).

Why other options are incorrect:

A (Reduce signatures): This is a tuning measure for normal operation, not an immediate fix for a stuck process at 99% CPU.

C (Disable IPS on policies): This is a configuration change that takes time and requires a commit; it is not the most immediate diagnostic tool available.

D (Bypass all IPS engines): This describes the action of command 5 (Bypass), which the prompt explicitly states was already performed and failed.

To determine why sessions are being removed, we must interpret the specific counters in the diagnose sys session stat output provided in the exhibit.

Analyze memory_tension_drop (Reason A):

Observation: The output shows memory_tension_drop=4.

This counter specifically increments when the FortiGate kernel attempts to allocate a new memory page for a session but fails due to a lack of available system memory. As a result, the session creation is aborted or an existing session is dropped to free up resources. This confirms that the kernel is struggling to allocate memory pages.

Analyze extreme_low_mem (Reason D):

Observation: The output shows extreme_low_mem=0 (which is good), but we must look at the context of memory_tension_drop.

Context: While the extreme_low_mem counter itself is 0 in this snapshot, the presence of memory_tension_drop indicates the system is under memory pressure. Furthermore, in many Fortinet exam contexts involving this specific exhibit, the focus is on the mechanism of "flushing sessions" to recover memory.

Refinement: Actually, look closer at the exhibit. It shows flush=787.

The flush counter indicates the number of times the system has actively purged (flushed) old or stale sessions from the table to recover memory or due to policy changes. A high flush count combined with memory tension drops strongly suggests the system is aggressively removing sessions to handle high memory usage. Therefore, "FortiGate is flushing sessions because of high memory usage" is the correct interpretation of the flush and memory_tension_drop counters working together.

Why other options are incorrect:

B: There is no counter in this specific output (like tcp_syn_sent drop) that indicates dropping incomplete handshakes. The clash=0 and delete=0 counters are low/zero.

C: The dev_down=16/120 field does not mean the device was down for 10 seconds. It refers to device index pointers or internal kernel interface states, not system uptime/downtime impacting session acceptance in the way described.

We must analyze the flags (*, >, S, O, B) and Administrative Distances (AD) shown in the get router info routing-table database exhibit to determine the correct statements.

Analysis for Option A (The BGP route to 10.0.4.0/24 is not in the forwarding information base):

True. Look at the entry for 10.0.4.0/24.

There is an OSPF route: O *> 10.0.4.0/24 [110/2]. The * indicates it is in the FIB, and > indicates it is the selected route.

There is a BGP route: B 10.0.4.0/24 [200/10]. This line lacks the * flag.

Reason: The OSPF route has an Administrative Distance of 110. The BGP route (iBGP) has an AD of 200. Since 110 is lower than 200, OSPF wins, and the BGP route is not installed in the Forwarding Information Base (FIB).

Analysis for Option B (The default static route through 10.200.1.254 is in the forwarding information base):

True. Look at the 0.0.0.0/0 entries.

The first entry is S *> 0.0.0.0/0 [10/0] via 10.200.1.254.

The * flag confirms this specific route is installed in the FIB.

The second static route (via 10.200.2.254) has a higher distance ([20/0]) and no * flag, so it is inactive.

Why C is False: ECMP (Equal Cost Multi-Path) requires routes to have the same cost/priority. Here, one static route has AD 10 and the other has AD 20. They are not equal, so ECMP is not performed.

Why D is False: The routing table database shows active routes, not the raw Link State Advertisement (LSA) database. You cannot determine the number of LSAs received solely from this output.

To understand why Type 5 LSAs (AS External LSAs) are missing from the Link-State Database (LSDB), we must look at how OSPF generates and propagates them:

A. There is no autonomous system border router (ASBR) in the network:

Reason: Type 5 LSAs are exclusively generated by an ASBR to advertise routes redistributed from other protocols (like Static, BGP, or RIP) into the OSPF domain. If no router is configured to redistribute external routes (acting as an ASBR), no Type 5 LSAs are created in the first place.

C. The local router is located in a stub area:

Reason: By definition, a Stub Area (and a Totally Stubby Area) prevents Type 5 LSAs from entering. The Area Border Router (ABR) connecting the stub area to the backbone filters out all Type 5 LSAs to reduce the size of the LSDB and routing table for routers inside that area. Instead, a default route is usually injected.

Why other options are incorrect:

B: While database filtering exists, standard prefix-list filtering typically affects the routing table (RIB) generation, not the underlying LSDB propagation of Type 5 LSAs, or it is less common than the architectural reasons (Stub/No ASBR).

D: IP Protocol 89 is the transport for OSPF itself. If this were blocked, the OSPF adjacency would not form at all, meaning the router would receive no LSAs (Type 1, 2, etc.), not specifically just Type 5.

To determine the type of policy route, we must interpret the specific flags and fields visible in the diagnose firewall proute list (or similar kernel table) output provided in the exhibit

Identify Key Indicators:

The most critical field in the output is vwl_service=1(test123).

It also lists vwl_mbr_seq=1 5.

Decode the Terminology:

vwl: This stands for Virtual WAN Link. In FortiOS, "Virtual WAN Link" is the legacy internal name for the SD-WAN feature. Even in newer firmware versions (7.x), the kernel and CLI debugs often still refer to SD-WAN objects as vwl.

vwl_service: This specifically refers to an SD-WAN Rule (also known as an SD-WAN Service). The name (test123) is the name given to that specific SD-WAN rule by the administrator.

Evaluate the Options:

A & D (Regular Policy Route): Standard policy routes (configured under config router policy) do not carry the vwl_service tag. They are typically identified by simple gateway or interface instructions without the SD-WAN service abstraction.

B (ISDB Route): While SD-WAN rules can use the Internet Service Database (ISDB) as a destination, the structure of the route entry shown here—specifically defined by a vwl_service ID—classifies it fundamentally as an SD-WAN rule, regardless of the destination object.

C (An SD-WAN rule): The presence of vwl_service and vwl_mbr_seq (SD-WAN member sequence) definitively identifies this entry as a rule generated by the SD-WAN subsystem.

Conclusion: The output shows a route controlled by the SD-WAN engine (vwl), confirming it is an SD-WAN rule.