- A
The NAT command is missing the 'vrf A' keyword; it should be ip nat inside source list 100 interface GigabitEthernet0/1 vrf A overload.
Why wrong: This command already includes the 'vrf A' keyword, so it is not missing. The problem lies elsewhere.
- B
The route leaking is misconfigured; use route-map to filter routes.
Why wrong: Route leaking is working correctly since hosts in VRF A can ping hosts in VRF B. The failure occurs only when NAT is applied, indicating the issue is with NAT configuration.
- C
The access-list 100 is blocking VRF B traffic.
Why wrong: The access-list may or may not block traffic, but the absence of NAT translations suggests the NAT command itself is not being applied, not necessarily a filtering issue.
- D
The interface GigabitEthernet0/1 is not in VRF A.
The most likely root cause is that the interface is not in VRF A, preventing NAT translations from being built.
NAT Not Working in VRF Due to Missing vrf Keyword
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.
In a multi-VRF environment, Router R1 is leaking routes between VRF A and VRF B using route-target import/export. Hosts in VRF A can ping hosts in VRF B, but traffic from VRF B to VRF A fails when NAT is applied on the VRF A egress interface. Configuration: ip nat inside source list 100 interface GigabitEthernet0/1 vrf A overload. Router R1 shows: show ip nat translations vrf A: no entries. What is the root cause?
Quick Answer
The answer is that the NAT command is missing the required 'vrf A' keyword, which must be explicitly added as in *ip nat inside source list 100 interface GigabitEthernet0/1 vrf A overload*. This is correct because in a multi-VRF environment, NAT operations are VRF-aware; without the *vrf* keyword appended to the NAT configuration, the router applies the translation only to the global routing table, not to the specified VRF. As a result, traffic from VRF B to VRF A bypasses translation entirely, causing asymmetric routing or unreachability even when route leaking is working. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of VRF-aware services and the common trap of assuming NAT inherits the VRF context from the interface. A reliable memory tip: "NAT needs its own VRF tag—if you forget the keyword, the translation is deferred."
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 interface GigabitEthernet0/1 is not in VRF A.
The issue is that interface GigabitEthernet0/1 is not in VRF A. For the NAT command 'ip nat inside source list 100 interface GigabitEthernet0/1 vrf A overload' to work, the interface must be part of VRF A. If it is not, the NAT translations will not be created, as seen in the output 'show ip nat translations vrf A: no entries'. Ensure the interface is configured with 'ip vrf forwarding A' to place it in the correct VRF.
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.
- ✗
The NAT command is missing the 'vrf A' keyword; it should be ip nat inside source list 100 interface GigabitEthernet0/1 vrf A overload.
Why it's wrong here
This command already includes the 'vrf A' keyword, so it is not missing. The problem lies elsewhere.
- ✗
The route leaking is misconfigured; use route-map to filter routes.
Why it's wrong here
Route leaking is working correctly since hosts in VRF A can ping hosts in VRF B. The failure occurs only when NAT is applied, indicating the issue is with NAT configuration.
- ✗
The access-list 100 is blocking VRF B traffic.
Why it's wrong here
The access-list may or may not block traffic, but the absence of NAT translations suggests the NAT command itself is not being applied, not necessarily a filtering issue.
- ✓
The interface GigabitEthernet0/1 is not in VRF A.
Why this is correct
The most likely root cause is that the interface is not in VRF A, preventing NAT translations from being built.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often assume that including the 'vrf' keyword in the NAT command is sufficient, but they overlook that the interface must also belong to that VRF. This question tests that nuance.
Trap categories for this question
Keyword trap
This command already includes the 'vrf A' keyword, so it is not missing. The problem lies elsewhere.
Command / output trap
This command already includes the 'vrf A' keyword, so it is not missing. The problem lies elsewhere.
Detailed technical explanation
How to think about this question
In a multi-VRF environment, NAT must be explicitly tied to a VRF using the 'vrf' keyword in the NAT command to ensure that the NAT process operates within the correct VRF context. Without this, the router's NAT engine does not associate translations with the VRF, leading to no entries in 'show ip nat translations vrf A' and failure of return traffic. This is critical when VRF-aware NAT is used for inter-VRF traffic, as the NAT table is VRF-specific.
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
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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: The interface GigabitEthernet0/1 is not in VRF A. — The issue is that interface GigabitEthernet0/1 is not in VRF A. For the NAT command 'ip nat inside source list 100 interface GigabitEthernet0/1 vrf A overload' to work, the interface must be part of VRF A. If it is not, the NAT translations will not be created, as seen in the output 'show ip nat translations vrf A: no entries'. Ensure the interface is configured with 'ip vrf forwarding A' to place it in the correct VRF.
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.
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Last reviewed: Jul 4, 2026
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