NSE7 Advanced VPN and Zero Trust Practice Question
This NSE7 practice question tests your understanding of advanced vpn and zero trust. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network administrator is troubleshooting an IPsec VPN between two FortiGates. The phase1 is up, but phase2 keeps failing to establish. The administrator runs 'diagnose vpn ike log' and sees: 'no proposal chosen'. Both sides have the same phase2 configuration: AES256-SHA256, DH group 14, 3600 seconds lifetime. What is the MOST likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Why wrong: NAT-T affects phase1 and encapsulation, not phase2 proposal matching.
B
The IKE version is different on each side
Why wrong: If phase1 is established, IKE version matches.
C
The phase2 local and remote subnets do not match on both sides
The 'no proposal chosen' error in phase2 usually indicates a mismatch in the traffic selectors (subnets). Both sides must have mirroring subnet definitions.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The phase2 local and remote subnets do not match on both sides
Even if the encryption/authentication proposals match, a common issue is a mismatch in the local and remote subnets (selectors). The phase2 negotiation requires matching traffic selectors. If one side has 192.168.1.0/24 and the other has 10.0.0.0/8, the proposals will be rejected. Option D is correct.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 NAT traversal setting is inconsistent
Why it's wrong here
NAT-T affects phase1 and encapsulation, not phase2 proposal matching.
✗
The IKE version is different on each side
Why it's wrong here
If phase1 is established, IKE version matches.
✓
The phase2 local and remote subnets do not match on both sides
Why this is correct
The 'no proposal chosen' error in phase2 usually indicates a mismatch in the traffic selectors (subnets). Both sides must have mirroring subnet definitions.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related NSE7 subnetting questions on CIDR, address ranges, and subnet selection.
Advanced VPN and Zero Trust — This question tests Advanced VPN and Zero Trust — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The phase2 local and remote subnets do not match on both sides — Even if the encryption/authentication proposals match, a common issue is a mismatch in the local and remote subnets (selectors). The phase2 negotiation requires matching traffic selectors. If one side has 192.168.1.0/24 and the other has 10.0.0.0/8, the proposals will be rejected. Option D is correct.
What should I do if I get this NSE7 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related NSE7 subnetting questions on CIDR, address ranges, and subnet selection.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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