Question 168 of 2,152

NAT and PAT →hardMultiple SelectObjective-mapped

300-410 NAT and PAT Practice Question

This 300-410 practice question tests your understanding of nat and pat. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.

An engineer must configure NAT so that inside hosts (192.168.1.0/24) are translated to a public IP pool (203.0.113.1-203.0.113.10) when accessing the Internet, but must NOT translate traffic destined to a VPN subnet (10.10.10.0/24) reachable via the same outside interface. Which TWO configuration steps are required? (Choose TWO.)

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "NOT"
Why it matters: Negative qualifier — you are looking for the one option that does NOT apply. Most options will be true; only one is false for this scenario.

A
Create an ACL that denies 10.10.10.0 0.0.0.255 and permits any, then reference it in a route map with 'match ip address'.
Correct. The ACL denies the VPN subnet, so the route map will not match traffic to that destination, thus exempting it from NAT.
B
Apply 'ip nat inside source list 1 interface GigabitEthernet0/0 overload' where ACL 1 permits 192.168.1.0 0.0.0.255.
Why wrong: Incorrect. This would translate all traffic from 192.168.1.0/24, including traffic to the VPN subnet, which is not desired.
C
Use 'ip nat inside source route-map RMAP pool POOL' where the route map matches the ACL from step A.
Correct. The route map uses the ACL to selectively translate only traffic not denied (i.e., not destined to VPN).
D
Configure 'ip nat inside source static 192.168.1.1 203.0.113.1' for each host to ensure translation.
Why wrong: Incorrect. Static NAT would require individual entries and would still translate traffic to the VPN subnet unless additional filtering is applied.
E
Apply 'ip access-group 100 in' on the inside interface to block traffic to the VPN subnet.
Why wrong: Incorrect. Blocking traffic is not the goal; the goal is to allow traffic but not translate it.

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

✓

Create an ACL that denies 10.10.10.0 0.0.0.255 and permits any, then reference it in a route map with 'match ip address'.

Option A is correct because it creates an ACL that denies the VPN subnet (10.10.10.0/24) and permits all other traffic, which is then referenced in a route map. This route map is used with 'ip nat inside source route-map RMAP pool POOL' to ensure that traffic destined to the VPN subnet is NOT translated, while all other traffic (including Internet-bound traffic) is translated using the public IP pool. This approach leverages route-map matching to selectively bypass NAT for specific destinations.

Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Create an ACL that denies 10.10.10.0 0.0.0.255 and permits any, then reference it in a route map with 'match ip address'.
Why this is correct
Correct. The ACL denies the VPN subnet, so the route map will not match traffic to that destination, thus exempting it from NAT.
Clue confirmation
The clue word "NOT" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Apply 'ip nat inside source list 1 interface GigabitEthernet0/0 overload' where ACL 1 permits 192.168.1.0 0.0.0.255.
Why it's wrong here
Incorrect. This would translate all traffic from 192.168.1.0/24, including traffic to the VPN subnet, which is not desired.
✓
Use 'ip nat inside source route-map RMAP pool POOL' where the route map matches the ACL from step A.
Why this is correct
Correct. The route map uses the ACL to selectively translate only traffic not denied (i.e., not destined to VPN).
Clue confirmation
The clue word "NOT" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Configure 'ip nat inside source static 192.168.1.1 203.0.113.1' for each host to ensure translation.
Why it's wrong here
Incorrect. Static NAT would require individual entries and would still translate traffic to the VPN subnet unless additional filtering is applied.
✗
Apply 'ip access-group 100 in' on the inside interface to block traffic to the VPN subnet.
Why it's wrong here
Incorrect. Blocking traffic is not the goal; the goal is to allow traffic but not translate it.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that an ACL in 'ip nat inside source list' can filter by destination, when in fact it only matches source addresses, so candidates may incorrectly choose Option B without realizing it would translate VPN-bound traffic.

Detailed technical explanation

How to think about this question

Under the hood, NAT route-map matching uses the 'match ip address' command to evaluate the destination IP of the packet (since the route map is applied to the 'outside' direction by default in NAT context). The ACL in Option A denies the VPN subnet, so packets destined to 10.10.10.0/24 do not match the route-map permit condition, and thus NAT is skipped. This is distinct from using an ACL in 'ip nat inside source list', which matches only the source IP; route-map NAT allows finer control based on destination, which is critical for split-tunneling scenarios in VPN deployments.

KKey Concepts to Remember

Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.

TExam Day Tips

Watch for words such as best, first, most likely and least administrative effort.
Review why wrong options are wrong, not only why the correct option is correct.

Key takeaway

Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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 — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: Create an ACL that denies 10.10.10.0 0.0.0.255 and permits any, then reference it in a route map with 'match ip address'. — Option A is correct because it creates an ACL that denies the VPN subnet (10.10.10.0/24) and permits all other traffic, which is then referenced in a route map. This route map is used with 'ip nat inside source route-map RMAP pool POOL' to ensure that traffic destined to the VPN subnet is NOT translated, while all other traffic (including Internet-bound traffic) is translated using the public IP pool. This approach leverages route-map matching to selectively bypass NAT for specific destinations.

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

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "NOT". Negative qualifier — you are looking for the one option that does NOT apply. Most options will be true; only one is false for this scenario.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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