The answer is to correct the ACL to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and add the 'overload' keyword to the PAT command. This fixes the broken NAT configuration because the ACL must match the actual inside LAN subnet for traffic to be translated, the outside interface must be correctly designated for the router to apply translations to outbound packets, and the 'overload' keyword is mandatory for Port Address Translation to enable many-to-one mapping using unique port numbers. On the CCNA 200-301 v2 exam, NAT troubleshooting tests your ability to verify interface roles, ACL logic, and the PAT syntax—a common trap is forgetting that without 'overload', the router defaults to one-to-one dynamic NAT, which fails for multiple hosts. A reliable memory tip is "ACL matches the inside, outside is the public side, and overload makes PAT work."
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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.
Network Topology
You are connected to R1. The network has two routers: R1 (192.168.1.0/24 LAN) and R2 (Internet gateway). R1's inside LAN (192.168.1.0/24) must be translated to the public IP 203.0.113.1 using PAT (NAT overload) for Internet access. Additionally, the server at 192.168.1.100 must be reachable from the Internet via static NAT to 203.0.113.5. The current configuration is broken. Identify and fix the issues so that both PAT and static NAT work correctly.
R1# show running-config | section ip nat
ip nat inside source list 10 interface GigabitEthernet0/1 overload
ip nat inside source static 192.168.1.100 203.0.113.5
!
access-list 10 permit 10.0.0.0 0.255.255.255
!
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
interface GigabitEthernet0/1
ip address 203.0.113.2 255.255.255.248
ip nat inside
!
interface Serial0/0/0
ip address 10.0.0.1 255.255.255.252
ip nat outside
!
A
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and ensure the PAT command includes 'overload'.
This is correct because the ACL must match the inside LAN (192.168.1.0/24) for PAT to translate traffic. The inside interface for the public IP must be marked as 'ip nat outside' to allow translation of return traffic. The 'overload' keyword enables PAT (port address translation).
B
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat inside', and ensure the PAT command includes 'overload'.
Why wrong: This is incorrect because G0/1 should be 'ip nat outside', not 'ip nat inside'. The interface facing the public IP must be marked as outside for NAT to work correctly.
C
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and remove the 'overload' keyword from the PAT command.
Why wrong: This is incorrect because removing 'overload' would disable PAT, meaning only one inside host could use the public IP at a time. The requirement is for PAT (overload) to allow multiple hosts.
D
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat inside', and remove the 'overload' keyword from the PAT command.
Why wrong: This is incorrect because it combines two errors: G0/1 should be 'outside' and 'overload' is required for PAT. This configuration would not allow proper NAT operation.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and ensure the PAT command includes 'overload'.
The configuration had three issues: 1) ACL 10 permitted 10.0.0.0/8 instead of the actual inside subnet 192.168.1.0/24, so no traffic matched PAT. 2) The PAT command was missing the 'overload' keyword, which is required for Port Address Translation; without it, the device attempts one-to-one dynamic NAT. 3) The interface facing the public network (G0/1) was incorrectly configured as 'ip nat inside' instead of 'ip nat outside'. The fix is to correct the ACL to permit 192.168.1.0 0.0.0.255, ensure the PAT command includes 'overload', and change G0/1 to 'ip nat outside'.
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.
✓
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and ensure the PAT command includes 'overload'.
Why this is correct
This is correct because the ACL must match the inside LAN (192.168.1.0/24) for PAT to translate traffic. The inside interface for the public IP must be marked as 'ip nat outside' to allow translation of return traffic. The 'overload' keyword enables PAT (port address translation).
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat inside', and ensure the PAT command includes 'overload'.
Why it's wrong here
This is incorrect because G0/1 should be 'ip nat outside', not 'ip nat inside'. The interface facing the public IP must be marked as outside for NAT to work correctly.
✗
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and remove the 'overload' keyword from the PAT command.
Why it's wrong here
This is incorrect because removing 'overload' would disable PAT, meaning only one inside host could use the public IP at a time. The requirement is for PAT (overload) to allow multiple hosts.
✗
Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat inside', and remove the 'overload' keyword from the PAT command.
Why it's wrong here
This is incorrect because it combines two errors: G0/1 should be 'outside' and 'overload' is required for PAT. This configuration would not allow proper NAT operation.
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.
✓Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and ensure the PAT command includes 'overload'.Correct answer▾
Why this is correct
This is correct because the ACL must match the inside LAN (192.168.1.0/24) for PAT to translate traffic. The inside interface for the public IP must be marked as 'ip nat outside' to allow translation of return traffic. The 'overload' keyword enables PAT (port address translation).
✗Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat inside', and ensure the PAT command includes 'overload'.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the interface with the public IP (203.0.113.1) must be configured as 'ip nat outside', not 'ip nat inside'. Marking it as inside would cause asymmetric NAT behavior and break translation.
Why candidates choose this
Candidates might think both interfaces should be 'inside' because they are both on the router, but the outside interface is the one facing the public network.
✗Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and remove the 'overload' keyword from the PAT command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that PAT requires the 'overload' keyword. Without it, the router performs dynamic NAT (one-to-one translation), which would not support multiple hosts sharing a single public IP.
Why candidates choose this
Candidates might think 'overload' is optional or that it causes issues with static NAT, but both can coexist; the keyword is necessary for PAT.
✗Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat inside', and remove the 'overload' keyword from the PAT command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual errors are: (1) the interface with the public IP must be 'ip nat outside', and (2) PAT requires the 'overload' keyword. Both are violated here.
Why candidates choose this
Candidates might think that removing 'overload' simplifies the configuration and that both interfaces can be 'inside', but this misunderstands NAT interface roles and the need for PAT.
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.
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: Change ACL 10 to permit 192.168.1.0 0.0.0.255, change G0/1 to 'ip nat outside', and ensure the PAT command includes 'overload'. — The configuration had three issues: 1) ACL 10 permitted 10.0.0.0/8 instead of the actual inside subnet 192.168.1.0/24, so no traffic matched PAT. 2) The PAT command was missing the 'overload' keyword, which is required for Port Address Translation; without it, the device attempts one-to-one dynamic NAT. 3) The interface facing the public network (G0/1) was incorrectly configured as 'ip nat inside' instead of 'ip nat outside'. The fix is to correct the ACL to permit 192.168.1.0 0.0.0.255, ensure the PAT command includes 'overload', and change G0/1 to 'ip nat outside'.
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.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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. You are connected to R1 via the console. R1's GigabitEthernet0/0 (10.0.0.1/30) connects to an ISP router at 10.0.0.2/30. The internal network has a web server at 192.168.1.10 and a mail server at 192.168.1.20. You need to configure NAT so that internal hosts can access the internet (PAT overload) and external users can reach the web server via public IP 203.0.113.10 and the mail server via public IP 203.0.113.11. The inside interface is GigabitEthernet0/1 (192.168.1.1/24) and the outside interface is GigabitEthernet0/0.
hard
✓ A.ip access-list standard PERMIT_INTERNAL permit 192.168.1.0 0.0.0.255
interface GigabitEthernet0/1
ip nat inside
interface GigabitEthernet0/0
ip nat outside
ip nat inside source list PERMIT_INTERNAL interface GigabitEthernet0/0 overload
ip nat inside source static tcp 192.168.1.10 80 203.0.113.10 80 extendable
ip nat inside source static tcp 192.168.1.20 25 203.0.113.11 25 extendable
B.ip access-list standard PERMIT_INTERNAL permit 192.168.1.0 0.0.0.255
interface GigabitEthernet0/1
ip nat outside
interface GigabitEthernet0/0
ip nat inside
ip nat inside source list PERMIT_INTERNAL interface GigabitEthernet0/0 overload
ip nat inside source static tcp 192.168.1.10 80 203.0.113.10 80
ip nat inside source static tcp 192.168.1.20 25 203.0.113.11 25
C.ip access-list standard PERMIT_INTERNAL permit 192.168.1.0 0.0.0.255
interface GigabitEthernet0/1
ip nat inside
interface GigabitEthernet0/0
ip nat outside
ip nat inside source list PERMIT_INTERNAL interface GigabitEthernet0/0 overload
ip nat inside source static 192.168.1.10 203.0.113.10
ip nat inside source static 192.168.1.20 203.0.113.11
D.ip access-list standard PERMIT_INTERNAL permit 192.168.1.0 0.0.0.255
interface GigabitEthernet0/1
ip nat inside
interface GigabitEthernet0/0
ip nat outside
ip nat inside source list PERMIT_INTERNAL interface GigabitEthernet0/0 overload
ip nat outside source static tcp 203.0.113.10 80 192.168.1.10 80
ip nat outside source static tcp 203.0.113.11 25 192.168.1.20 25
Why A: The named standard ACL PERMIT_INTERNAL permits all internal hosts in 192.168.1.0/24. The 'ip nat inside source list PERMIT_INTERNAL interface GigabitEthernet0/0 overload' command enables PAT, translating internal addresses to the outside interface's IP. Static NAT entries map web and mail servers to public IPs with the 'extendable' keyword to allow both PAT and static NAT. Proper interface NAT direction (inside/outside) is crucial.
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