Question 1,132 of 2,152

NAT and PAT →mediumMultiple ChoiceObjective-mapped

Static NAT Port Forwarding — Using extendable Keyword | Cisco CCNP ENARSI 300-410 Explained

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.

Examine this configuration:

interface GigabitEthernet0/0
 ip address 10.0.0.1 255.255.255.0
 ip nat inside

interface GigabitEthernet0/1
 ip address 198.51.100.1 255.255.255.0
 ip nat outside

ip nat inside source static tcp 10.0.0.10 80 198.51.100.10 8080 extendable

Which statement is true?

A
All traffic from 10.0.0.10 is translated to 198.51.100.10.
Why wrong: Only TCP port 80 is translated; other ports are not affected.
B
Incoming traffic to 198.51.100.10:8080 is forwarded to 10.0.0.10:80.
Static NAT/PAT maps the outside address/port to the inside address/port bidirectionally.
C
The 'extendable' keyword is invalid for static NAT.
Why wrong: 'extendable' is valid and allows overlapping static translations.
D
This translation will not work unless 'ip nat inside source list' is also configured.
Why wrong: Static NAT is independent and does not require a dynamic NAT rule.

Full breakdown with real-world context →

Quick Answer

The correct answer is that incoming traffic to 198.51.100.10:8080 is forwarded to 10.0.0.10:80. This static NAT port forwarding configuration maps an inside local host and port to a specific outside global address and port, and the `extendable` keyword permits multiple static translations to share the same outside IP address by allowing the router to create additional NAT entries as needed. On the Cisco CCNP ENARSI 300-410 exam, this concept tests your understanding of how static NAT with port forwarding differs from dynamic NAT, and the `extendable` keyword is a common trap—many candidates mistakenly think it is only for dynamic translations or that it disables port forwarding. Remember the memory tip: “extendable extends the pool of translations, not the port range,” so think of it as enabling multiple inside hosts to use the same outside IP by differentiating on port numbers.

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

✓

Incoming traffic to 198.51.100.10:8080 is forwarded to 10.0.0.10:80.

The configuration uses a static NAT with TCP port translation (also known as NAT with port forwarding). The command `ip nat inside source static tcp 10.0.0.10 80 198.51.100.10 8080 extendable` creates a one-to-one mapping between the inside local address/port (10.0.0.10:80) and the inside global address/port (198.51.100.10:8080). This means any incoming packet destined to 198.51.100.10 on TCP port 8080 will have its destination translated to 10.0.0.10 port 80, and the response traffic is reverse-translated. Option B correctly describes this behavior.

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.

✗
All traffic from 10.0.0.10 is translated to 198.51.100.10.
Why it's wrong here
Only TCP port 80 is translated; other ports are not affected.
✓
Incoming traffic to 198.51.100.10:8080 is forwarded to 10.0.0.10:80.
Why this is correct
Static NAT/PAT maps the outside address/port to the inside address/port bidirectionally.
Related concept
Read the scenario before looking for a memorised answer.
✗
The 'extendable' keyword is invalid for static NAT.
Why it's wrong here
'extendable' is valid and allows overlapping static translations.
✗
This translation will not work unless 'ip nat inside source list' is also configured.
Why it's wrong here
Static NAT is independent and does not require a dynamic NAT rule.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that static NAT translates all traffic from an inside host, when in fact a static NAT with port specification only translates traffic matching that specific protocol and port, leaving other traffic untranslated.

Detailed technical explanation

How to think about this question

Under the hood, the 'extendable' keyword modifies the NAT translation table behavior to allow overlapping inside global addresses by using port numbers as part of the translation key. Without 'extendable', a static NAT entry would consume the entire global IP address, preventing other static entries from using the same global IP. This is critical in real-world scenarios where you need to map multiple internal servers (e.g., web, SSH, mail) to different ports on a single public IP address, effectively implementing port forwarding via static NAT.

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: Incoming traffic to 198.51.100.10:8080 is forwarded to 10.0.0.10:80. — The configuration uses a static NAT with TCP port translation (also known as NAT with port forwarding). The command `ip nat inside source static tcp 10.0.0.10 80 198.51.100.10 8080 extendable` creates a one-to-one mapping between the inside local address/port (10.0.0.10:80) and the inside global address/port (198.51.100.10:8080). This means any incoming packet destined to 198.51.100.10 on TCP port 8080 will have its destination translated to 10.0.0.10 port 80, and the response traffic is reverse-translated. Option B correctly describes this behavior.

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.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

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Same concept, more angles

1 more ways this is tested on 300-410

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. Which statement accurately describes the behavior of the ip nat inside source static command when configuring static NAT for a single inside host?

easy

A.It dynamically allocates the global address from a pool and removes the entry after an idle timeout.
✓ B.It creates a permanent mapping that remains in the NAT table until the configuration is removed.
C.It requires the use of an access list to define which traffic is translated.
D.It translates only TCP and UDP traffic by default.

Why B: The `ip nat inside source static` command creates a permanent one-to-one mapping between an inside local IP address and an inside global IP address. This static entry remains in the NAT table indefinitely until the administrator explicitly removes it with the `no ip nat inside source static` command, making option B correct.

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