The answer is that the 'no matching policy' message indicates the traffic is dropped by the implicit deny rule. This occurs because the FortiGate’s debug flow engine processes packets sequentially against configured firewall policies, and when no explicit policy permits the traffic from source 192.168.1.10 to destination 8.8.8.8, the session is terminated by the default deny-all rule at the end of the policy list. On the Fortinet NSE 4 Network Security Professional NSE4 exam, this concept tests your understanding of policy evaluation order and the critical role of implicit deny—a common trap is confusing this with a routing issue or an interface misconfiguration, but the debug output explicitly points to a missing allow policy. A helpful memory tip: "No match means no permit, so the packet takes a hit from the implicit pit."
NSE4 Firewall Policies and NAT Practice Question
This NSE4 practice question tests your understanding of firewall policies and nat. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You run the following CLI command on a FortiGate:
# diagnose debug flow filter saddr 192.168.1.10
# diagnose debug flow show function enable
# diagnose debug enable
You then initiate a ping from 192.168.1.10 to 8.8.8.8. The output shows 'no matching policy'. What does this indicate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The traffic is dropped by the implicit deny rule
The 'no matching policy' message indicates that the traffic did not match any firewall policy, likely because there is no policy allowing the traffic from that source to the destination.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The traffic is being NAT'd but not logged
Why it's wrong here
NAT is applied after policy match; no match means no NAT.
✗
The debug filter is incorrectly configured
Why it's wrong here
The filter appears correct.
✗
There is a routing issue preventing the traffic
Why it's wrong here
Routing is checked after policy match; if no policy match, routing is not considered.
✓
The traffic is dropped by the implicit deny rule
Why this is correct
Since no policy matches, the implicit deny at the end drops the traffic.
Related concept
Static NAT maps one inside address to one outside address.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
Firewall Policies and NAT — This question tests Firewall Policies and NAT — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: The traffic is dropped by the implicit deny rule — The 'no matching policy' message indicates that the traffic did not match any firewall policy, likely because there is no policy allowing the traffic from that source to the destination.
What should I do if I get this NSE4 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related NSE4 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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