The answer is that the ip nat inside command is missing from the LAN-facing interface. This is the most likely reason for empty NAT translations because dynamic translations, such as those used for PAT overloading, only appear in the output of show ip nat translations when the router identifies an interface as part of the inside network. Without the ip nat inside command configured on the GigabitEthernet0/0 interface receiving traffic from the 192.168.1.0/24 LAN, the router never evaluates those packets for NAT, leaving the translation table populated only with static entries. On the CCNA 200-301 v2 exam, this scenario tests your understanding of the fundamental NAT configuration sequence: you must explicitly mark both the inside and outside interfaces. A common trap is assuming that a static NAT entry alone proves NAT is working, but static entries are independent of interface commands. Remember the mnemonic "Inside In, Outside Out" — the inside command must be on the interface where inside hosts send traffic, or your dynamic translations will stay empty.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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
--- 209.165.200.225 192.168.1.10 --- ---
--- 209.165.200.226 192.168.1.11 --- ---
--- 209.165.200.227 192.168.1.12 --- ---
--- 209.165.200.228 192.168.1.13 --- ---
--- 209.165.200.229 192.168.1.14 --- ---
--- 209.165.200.230 192.168.1.15 --- ---
--- 209.165.200.231 192.168.1.16 --- ---
--- 209.165.200.232 192.168.1.17 --- ---
Refer to the exhibit. An administrator has configured NAT on router R1 to allow hosts on the 192.168.1.0/24 LAN to access the Internet. However, users report that they cannot reach external websites. The administrator runs the show ip nat translations command. What is the most likely reason for the problem?
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.
R1# show ip nat translations
Pro Inside global Inside local Outside local Outside global
--- 209.165.200.225 192.168.1.10 --- ---
--- 209.165.200.226 192.168.1.11 --- ---
--- 209.165.200.227 192.168.1.12 --- ---
--- 209.165.200.228 192.168.1.13 --- ---
--- 209.165.200.229 192.168.1.14 --- ---
--- 209.165.200.230 192.168.1.15 --- ---
--- 209.165.200.231 192.168.1.16 --- ---
--- 209.165.200.232 192.168.1.17 --- ---
A
The access list used for dynamic NAT does not match the LAN subnet.
Why wrong: An incorrect access list would prevent matches for dynamic NAT, but the dynamic NAT process itself would still be active and could show translations for other traffic. However, the exhibit shows no dynamic entries at all, indicating the NAT process on the inside interface is not even running.
B
The ip nat outside command is missing from the WAN interface.
Why wrong: If the WAN interface lacked ip nat outside, static NAT entries would also fail to appear (or traffic would not be translated correctly). The static entries in the table confirm that the outside interface is marked correctly.
C
The ip nat inside source static commands have incorrect IP addresses.
Why wrong: The static NAT entries are displaying correctly with valid IP pairings, so the static mappings themselves are not the issue. Incorrect IP addresses would still show dynamic entries for the LAN hosts if dynamic NAT were configured correctly.
D
The ip nat inside command is missing from the LAN-facing interface.
The output reveals that only static NAT translations are active; no dynamic entries exist. For the router to process packets from the LAN under NAT, the interface connected to the LAN must be configured with ip nat inside. Its absence stops all dynamic address translation, leaving only the manually configured static entries.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The ip nat inside command is missing from the LAN-facing interface.
The output shows only static NAT entries (protocol column "---") with no dynamic translations. The presence of static entries does not depend on the dynamic NAT configuration. For dynamic NAT (like PAT overloading) to create translations for outbound traffic, the interface that receives packets from the inside hosts must have the ip nat inside command. Because the LAN-facing interface is missing this command, no packets from 192.168.1.0/24 are evaluated for NAT, resulting in an empty dynamic translation table and connectivity failure.
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 access list used for dynamic NAT does not match the LAN subnet.
Why it's wrong here
An incorrect access list would prevent matches for dynamic NAT, but the dynamic NAT process itself would still be active and could show translations for other traffic. However, the exhibit shows no dynamic entries at all, indicating the NAT process on the inside interface is not even running.
✗
The ip nat outside command is missing from the WAN interface.
Why it's wrong here
If the WAN interface lacked ip nat outside, static NAT entries would also fail to appear (or traffic would not be translated correctly). The static entries in the table confirm that the outside interface is marked correctly.
✗
The ip nat inside source static commands have incorrect IP addresses.
Why it's wrong here
The static NAT entries are displaying correctly with valid IP pairings, so the static mappings themselves are not the issue. Incorrect IP addresses would still show dynamic entries for the LAN hosts if dynamic NAT were configured correctly.
✓
The ip nat inside command is missing from the LAN-facing interface.
Why this is correct
The output reveals that only static NAT translations are active; no dynamic entries exist. For the router to process packets from the LAN under NAT, the interface connected to the LAN must be configured with ip nat inside. Its absence stops all dynamic address translation, leaving only the manually configured static entries.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
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 ip nat inside command is missing from the LAN-facing interface.Correct answer▾
Why this is correct
The output reveals that only static NAT translations are active; no dynamic entries exist. For the router to process packets from the LAN under NAT, the interface connected to the LAN must be configured with ip nat inside. Its absence stops all dynamic address translation, leaving only the manually configured static entries.
✗The access list used for dynamic NAT does not match the LAN subnet.Wrong answer — click to see why▾
Why this is wrong here
Candidates think any absence of dynamic entries is due to ACL mismatch, overlooking the prerequisite that the inside interface must be configured with ip nat inside for NAT to function at all.
✗The ip nat outside command is missing from the WAN interface.Wrong answer — click to see why▾
Why this is wrong here
The presence of static NAT translations in the output indicates that the ip nat outside command is already applied on the WAN interface.
✗The ip nat inside source static commands have incorrect IP addresses.Wrong answer — click to see why▾
Why this is wrong here
Candidates may focus on the static entries, but the symptom is missing dynamic translations; bad static mappings would not prevent dynamic translations from appearing.
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
An incorrect access list would prevent matches for dynamic NAT, but the dynamic NAT process itself would still be active and could show translations for other traffic. However, the exhibit shows no dynamic entries at all, indicating the NAT process on the inside interface is not even running.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
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.
Network Services and Security — This question tests Network Services and Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: The ip nat inside command is missing from the LAN-facing interface. — The output shows only static NAT entries (protocol column "---") with no dynamic translations. The presence of static entries does not depend on the dynamic NAT configuration. For dynamic NAT (like PAT overloading) to create translations for outbound traffic, the interface that receives packets from the inside hosts must have the ip nat inside command. Because the LAN-facing interface is missing this command, no packets from 192.168.1.0/24 are evaluated for NAT, resulting in an empty dynamic translation table and connectivity failure.
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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