Question 1,366 of 2,152

NAT and PAT →mediumMultiple ChoiceObjective-mapped

300-410 NAT and PAT Practice Question

This 300-410 practice question tests your understanding of nat and pat. 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 engineer is troubleshooting connectivity from a host inside a corporate network to a public web server. The host has IP 10.1.1.10/24, and the router's outside interface is 203.0.113.1/24. The engineer configured a dynamic NAT pool (203.0.113.10-203.0.113.20) and an access list permitting 10.1.1.0/24. However, traffic from the host fails. A 'show ip nat translations' reveals no translations. 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.

Question 1mediummultiple choice

Read the full NAT/PAT explanation →

A
The NAT pool is exhausted.
Why wrong: Incorrect because the pool has 11 addresses, and only one host is trying to translate; no translations appear at all, not a pool exhaustion issue.
B
The 'ip nat inside' and 'ip nat outside' commands are misapplied on the interfaces.
Why wrong: Incorrect because if the interfaces are not correctly designated, translations might still appear but traffic would not flow; however, no translations at all suggests the ACL is the issue.
C
The access list used in the NAT configuration does not match the source IP of the host.
Correct because dynamic NAT requires the ACL to match the source; if the ACL is misconfigured (e.g., denies the subnet), no translations are created.
D
The host's default gateway is not the router's inside interface.
Why wrong: Incorrect because even if the gateway is wrong, the router would still see the traffic and attempt NAT if the ACL matches; no translations indicate a different issue.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The access list used in the NAT configuration does not match the source IP of the host.

If the access list does not match the source IP of the traffic, NAT will not create translations. The engineer must verify that the ACL permits the correct source subnet.

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 pool is exhausted.
Why it's wrong here
Incorrect because the pool has 11 addresses, and only one host is trying to translate; no translations appear at all, not a pool exhaustion issue.
✗
The 'ip nat inside' and 'ip nat outside' commands are misapplied on the interfaces.
Why it's wrong here
Incorrect because if the interfaces are not correctly designated, translations might still appear but traffic would not flow; however, no translations at all suggests the ACL is the issue.
✓
The access list used in the NAT configuration does not match the source IP of the host.
Why this is correct
Correct because dynamic NAT requires the ACL to match the source; if the ACL is misconfigured (e.g., denies the subnet), no translations are created.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The host's default gateway is not the router's inside interface.
Why it's wrong here
Incorrect because even if the gateway is wrong, the router would still see the traffic and attempt NAT if the ACL matches; no translations indicate a different issue.

Common exam traps

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 300-410 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this 300-410 question test?

NAT and PAT — This question tests NAT and PAT — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The access list used in the NAT configuration does not match the source IP of the host. — If the access list does not match the source IP of the traffic, NAT will not create translations. The engineer must verify that the ACL permits the correct source subnet.

What should I do if I get this 300-410 question wrong?

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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