The answer is that traffic from the 172.16.0.0/24 network is not translated and will be forwarded with its original source IP address. This occurs because the NAT ACL mismatch prevents the router from matching the 172.16.0.0/24 subnet against access-list 1, which only permits 192.168.1.0/24. In Cisco NAT configuration, the `ip nat inside source list` command ties translation eligibility directly to the ACL; any inside network not explicitly permitted by that ACL is simply not translated, even if the interface is configured as `ip nat inside`. On the CCNP ENARSI 300-410 exam, this scenario tests your understanding of how ACLs control NAT policy—a common trap is assuming that all inside interfaces automatically get translated, when in fact the ACL is the sole gatekeeper. A useful memory tip: “The ACL is the bouncer—if your network isn’t on the list, it doesn’t get translated.”
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.
Consider this partial configuration:
ip nat inside source list 1 interface GigabitEthernet0/1 overload
access-list 1 permit 192.168.1.0 0.0.0.255
!
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/1
ip address 203.0.113.1 255.255.255.0
ip nat outside
!
interface GigabitEthernet0/2
ip address 172.16.0.1 255.255.255.0
ip nat inside
What is true about traffic from the 172.16.0.0/24 network?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It is not translated and will be forwarded with its original source IP.
The ACL (access-list 1) only permits 192.168.1.0/24. Traffic from 172.16.0.0/24 is not matched and therefore not translated.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
It is translated using PAT to 203.0.113.1.
Why it's wrong here
The ACL does not include 172.16.0.0/24, so no translation occurs.
✓
It is not translated and will be forwarded with its original source IP.
Why this is correct
Traffic not matching the ACL is not subject to NAT; it is routed normally.
Related concept
Static NAT maps one inside address to one outside address.
✗
It is dropped because NAT is required for all inside interfaces.
Why it's wrong here
NAT is not mandatory; unmatched traffic is forwarded without translation.
✗
It is translated using a different pool because it is on a separate inside interface.
Why it's wrong here
No other NAT rule exists; the only rule uses ACL 1, which does not match 172.16.0.0/24.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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 300-410 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
NAT and PAT — This question tests NAT and PAT — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: It is not translated and will be forwarded with its original source IP. — The ACL (access-list 1) only permits 192.168.1.0/24. Traffic from 172.16.0.0/24 is not matched and therefore not translated.
What should I do if I get this 300-410 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 300-410 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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