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CCNA Practice Question: A network administrator has configured dynamic…

This 200-301 practice question tests your understanding of 200-301 exam topics. 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.

Exhibit

R1# show ip nat translations
Pro Inside global      Inside local       Outside local      Outside global
--- 203.0.113.10       192.168.1.10       ---                ---
--- 203.0.113.11       192.168.1.11       ---                ---
--- 203.0.113.12       192.168.1.12       ---                ---
--- 203.0.113.13       192.168.1.13       ---                ---
--- 203.0.113.14       192.168.1.14       ---                ---
--- 203.0.113.15       192.168.1.15       ---                ---
--- 203.0.113.16       192.168.1.16       ---                ---
--- 203.0.113.17       192.168.1.17       ---                ---
--- 203.0.113.18       192.168.1.18       ---                ---
--- 203.0.113.19       192.168.1.19       ---                ---
--- 203.0.113.20       192.168.1.20       ---                ---
--- 203.0.113.21       192.168.1.21       ---                ---
--- 203.0.113.22       192.168.1.22       ---                ---
--- 203.0.113.23       192.168.1.23       ---                ---
--- 203.0.113.24       192.168.1.24       ---                ---
--- 203.0.113.25       192.168.1.25       ---                ---
--- 203.0.113.26       192.168.1.26       ---                ---
--- 203.0.113.27       192.168.1.27       ---                ---
--- 203.0.113.28       192.168.1.28       ---                ---
--- 203.0.113.29       192.168.1.29       ---                ---
--- 203.0.113.30       192.168.1.30       ---                ---

A network administrator has configured dynamic NAT with overload (PAT) on a Cisco router to allow internal hosts to access the Internet. Internal hosts can ping external servers, but external hosts cannot initiate connections to any internal host. The administrator checks the NAT translations. What is the most likely cause of this behavior?

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 1hardmultiple choice
Full question →

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 router is configured for dynamic NAT without overload (PAT), so it assigns one public IP per inside host and does not allow inbound connections without a static mapping.

The show ip nat translations output shows many dynamic one-to-one translations (no protocol or port listed), indicating that dynamic NAT without overload is being used instead of PAT. The pool of public IPs (203.0.113.10-.30) is being exhausted by individual inside-to-outside mappings, leaving no room for PAT to reuse a single IP for multiple sessions. This prevents external hosts from initiating connections because dynamic NAT does not allow inbound unsolicited traffic unless a static entry exists. The fix is to enable overload (PAT) so that many inside hosts share a single public IP using different port numbers.

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 because it contains only 21 addresses, and more than 21 internal hosts are trying to access the Internet simultaneously.

    Why it's wrong here

    While pool exhaustion is possible, the output shows many translations already, and the symptom is that external hosts cannot initiate connections—a problem that would persist even with a larger pool if overload is not used.

  • ✓

    The router is configured for dynamic NAT without overload (PAT), so it assigns one public IP per inside host and does not allow inbound connections without a static mapping.

    Why this is correct

    The absence of protocol/port in the translations indicates one-to-one dynamic NAT without overload. This explains why internal hosts can initiate outbound traffic (they get a public IP) but external hosts cannot reach internal hosts (no return path).

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    CIDR notation defines the prefix length.

  • ✗

    The inside local addresses are not in the same subnet as the inside interface, causing asymmetric routing.

    Why it's wrong here

    The inside local addresses (192.168.1.x) are typical private IPs and are assumed to be correctly configured on the inside interface. The translations show them mapping to public IPs, so routing is likely symmetric.

  • ✗

    The outside global addresses are not routable on the Internet, so external hosts cannot send return traffic.

    Why it's wrong here

    The public IPs shown (203.0.113.x) are from the TEST-NET-3 range, which is not globally routable. However, this is a common documentation range used in examples; in a real network, these would be replaced with routable IPs. The question assumes they are routable for the scenario.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

✓The router is configured for dynamic NAT without overload (PAT), so it assigns one public IP per inside host and does not allow inbound connections without a static mapping.Correct answer▾

Why this is correct

The absence of protocol/port in the translations indicates one-to-one dynamic NAT without overload. This explains why internal hosts can initiate outbound traffic (they get a public IP) but external hosts cannot reach internal hosts (no return path).

✗The NAT pool is exhausted because it contains only 21 addresses, and more than 21 internal hosts are trying to access the Internet simultaneously.Wrong answer — click to see why▾

Why this is wrong here

This is a symptom of the real issue (no overload), but the root cause is the lack of PAT, not just pool size. Even with a larger pool, external-initiated traffic would still be blocked without static NAT or overload.

✗The inside local addresses are not in the same subnet as the inside interface, causing asymmetric routing.Wrong answer — click to see why▾

Why this is wrong here

There is no evidence of routing issues; the translations are working for outbound traffic. Asymmetric routing would cause connectivity problems in both directions, not just inbound.

✗The outside global addresses are not routable on the Internet, so external hosts cannot send return traffic.Wrong answer — click to see why▾

Why this is wrong here

Even if the IPs were non-routable, the symptom would be that internal hosts cannot reach external hosts, but they can. The problem is specifically with inbound connections, which points to NAT configuration, not IP routability.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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.

Trap categories for this question

  • Command / output trap

    While pool exhaustion is possible, the output shows many translations already, and the symptom is that external hosts cannot initiate connections—a problem that would persist even with a larger pool if overload is not used.

  • Scenario analysis trap

    The public IPs shown (203.0.113.x) are from the TEST-NET-3 range, which is not globally routable. However, this is a common documentation range used in examples; in a real network, these would be replaced with routable IPs. The question assumes they are routable for the scenario.

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 200-301 subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this 200-301 question test?

CIDR notation defines the prefix length.

What is the correct answer to this question?

The correct answer is: The router is configured for dynamic NAT without overload (PAT), so it assigns one public IP per inside host and does not allow inbound connections without a static mapping. — The show ip nat translations output shows many dynamic one-to-one translations (no protocol or port listed), indicating that dynamic NAT without overload is being used instead of PAT. The pool of public IPs (203.0.113.10-.30) is being exhausted by individual inside-to-outside mappings, leaving no room for PAT to reuse a single IP for multiple sessions. This prevents external hosts from initiating connections because dynamic NAT does not allow inbound unsolicited traffic unless a static entry exists. The fix is to enable overload (PAT) so that many inside hosts share a single public IP using different port numbers.

What should I do if I get this 200-301 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 200-301 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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