The answer is to correct the inside/outside interface assignments, fix the ACL to match the 192.168.1.0/24 LAN, and add the overload keyword to the PAT command. This is correct because PAT (NAT overload) allows multiple private hosts to share a single public IP by multiplexing traffic based on port numbers; the inside interface must face the LAN, the outside interface must face the WAN, and the access list must define the exact source network to be translated. On the CCNA 200-301 v2 exam, this scenario tests your ability to troubleshoot common PAT configuration errors, often presented as a simlet where you must identify swapped interfaces, a missing overload keyword, or a mismatched ACL—a classic trap is assuming the ACL is correct when it permits the wrong subnet. Remember the mnemonic "Inside LAN, Outside WAN, Overload for many, ACL for the plan" to keep the three fixes straight.
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. Configure PAT (NAT overload) so that hosts on the 192.168.1.0/24 LAN can access the Internet via the outside interface GigabitEthernet 0/1 with IP 203.0.113.2/29. The current configuration has an incorrect inside/outside interface assignment and a missing overload keyword. Fix all issues.
R1# show running-config | section ip nat
ip nat inside source list NAT_POOL interface GigabitEthernet0/1
ip nat inside source static tcp 192.168.1.10 80 203.0.113.3 80 extendable
!
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
ip nat outside
!
interface GigabitEthernet0/1
ip address 203.0.113.2 255.255.255.248
ip nat inside
!
access-list 10 permit 10.0.0.0 0.255.255.255
A
Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.
This is correct because it fixes all three issues: the inside/outside interface assignments are swapped, the ACL permits the wrong subnet, and the PAT command lacks the 'overload' keyword. The correct configuration ensures proper NAT operation.
B
Configure 'ip nat outside' on GigabitEthernet0/0, 'ip nat inside' on GigabitEthernet0/1, keep ACL 10 as is, and add 'overload' to the PAT command.
Why wrong: This is incorrect because it swaps the inside and outside interfaces incorrectly. The LAN interface should be inside, and the WAN interface should be outside. Also, the ACL still permits the wrong subnet.
C
Configure 'ip nat inside' on GigabitEthernet0/1, 'ip nat outside' on GigabitEthernet0/0, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.
Why wrong: This is incorrect because it assigns the inside interface to the WAN and the outside interface to the LAN, which is the opposite of what is needed. NAT will not function correctly.
D
Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, but do not add 'overload' to the PAT command.
Why wrong: This is incorrect because it omits the 'overload' keyword, which is necessary for PAT (port address translation) to allow multiple internal hosts to share a single public IP. Without 'overload', only one-to-one translation occurs.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.
Three issues exist: (1) The inside and outside interfaces are swapped — GigabitEthernet0/0 (LAN) should be 'ip nat inside' and GigabitEthernet0/1 (WAN) should be 'ip nat outside'. (2) The PAT command lacks the 'overload' keyword. (3) ACL 10 permits 10.0.0.0/8 but the inside subnet is 192.168.1.0/24; ACL must be corrected. Fix with 'interface GigabitEthernet0/0', 'ip nat inside', 'interface GigabitEthernet0/1', 'ip nat outside', 'ip nat inside source list 10 interface GigabitEthernet0/1 overload', and 'access-list 10 permit 192.168.1.0 0.0.0.255'.
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.
✓
Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.
Why this is correct
This is correct because it fixes all three issues: the inside/outside interface assignments are swapped, the ACL permits the wrong subnet, and the PAT command lacks the 'overload' keyword. The correct configuration ensures proper NAT operation.
Configure 'ip nat outside' on GigabitEthernet0/0, 'ip nat inside' on GigabitEthernet0/1, keep ACL 10 as is, and add 'overload' to the PAT command.
Why it's wrong here
This is incorrect because it swaps the inside and outside interfaces incorrectly. The LAN interface should be inside, and the WAN interface should be outside. Also, the ACL still permits the wrong subnet.
✗
Configure 'ip nat inside' on GigabitEthernet0/1, 'ip nat outside' on GigabitEthernet0/0, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.
Why it's wrong here
This is incorrect because it assigns the inside interface to the WAN and the outside interface to the LAN, which is the opposite of what is needed. NAT will not function correctly.
✗
Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, but do not add 'overload' to the PAT command.
Why it's wrong here
This is incorrect because it omits the 'overload' keyword, which is necessary for PAT (port address translation) to allow multiple internal hosts to share a single public IP. Without 'overload', only one-to-one translation occurs.
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.
✓Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.Correct answer▾
Why this is correct
This is correct because it fixes all three issues: the inside/outside interface assignments are swapped, the ACL permits the wrong subnet, and the PAT command lacks the 'overload' keyword. The correct configuration ensures proper NAT operation.
✗Configure 'ip nat outside' on GigabitEthernet0/0, 'ip nat inside' on GigabitEthernet0/1, keep ACL 10 as is, and add 'overload' to the PAT command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The inside/outside interface assignment is reversed; ACL 10 permits 10.0.0.0/8 instead of 192.168.1.0/24.
Why candidates choose this
Candidates pick this because they might think the outside interface is the LAN side, or they overlook the ACL issue.
✗Configure 'ip nat inside' on GigabitEthernet0/1, 'ip nat outside' on GigabitEthernet0/0, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The inside/outside interface assignment is reversed; the WAN interface should be outside, not inside.
Why candidates choose this
Candidates pick this because they might confuse which interface is inside and which is outside, or they think the 'inside' keyword refers to the internal network of the router.
✗Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, but do not add 'overload' to the PAT command.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The 'overload' keyword is missing, which is required for PAT to enable many-to-one translation.
Why candidates choose this
Candidates pick this because they might think that NAT overload is enabled by default or that the 'overload' keyword is optional 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.
Trap categories for this question
Keyword trap
This is incorrect because it omits the 'overload' keyword, which is necessary for PAT (port address translation) to allow multiple internal hosts to share a single public IP. Without 'overload', only one-to-one translation occurs.
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: Configure 'ip nat inside' on GigabitEthernet0/0, 'ip nat outside' on GigabitEthernet0/1, correct ACL 10 to permit 192.168.1.0 0.0.0.255, and add 'overload' to the PAT command. — Three issues exist: (1) The inside and outside interfaces are swapped — GigabitEthernet0/0 (LAN) should be 'ip nat inside' and GigabitEthernet0/1 (WAN) should be 'ip nat outside'. (2) The PAT command lacks the 'overload' keyword. (3) ACL 10 permits 10.0.0.0/8 but the inside subnet is 192.168.1.0/24; ACL must be corrected. Fix with 'interface GigabitEthernet0/0', 'ip nat inside', 'interface GigabitEthernet0/1', 'ip nat outside', 'ip nat inside source list 10 interface GigabitEthernet0/1 overload', and 'access-list 10 permit 192.168.1.0 0.0.0.255'.
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. A small office uses PAT for user Internet access. What mechanism does PAT use to allow many users to share one public address while keeping their sessions distinct?
hard
✓ A.Use transport-layer port values to distinguish multiple inside sessions behind one outside address.
B.Convert all inside hosts to the same private IP address.
C.Increase the size of the NAT pool to include multiple public addresses.
D.Configure static NAT mappings for each inside host.
Why A: PAT (Port Address Translation) distinguishes multiple inside sessions by rewriting the source port number for each connection while using the same public IP address. This transport-layer port translation allows many internal hosts to share one outside address without conflict. The correct answer identifies the use of port numbers, which is the core mechanism. Increasing the NAT pool or using static NAT would not enable sharing of a single public address. Changing private IPs to be identical or disabling routes are irrelevant to PAT's operation.
Variation 2. Match each NAT or address-related term to its most accurate description.
medium
✓ A.A one-to-one mapping between a private IP address and a public IP address, configured manually and remaining constant.
B.A many-to-one mapping where multiple private IP addresses share a single public IP address, distinguished by port numbers.
C.A dynamic mapping where private IP addresses are translated to public IP addresses from a pool, without port translation.
D.A special IP address (127.0.0.1) used by a host to send traffic to itself for testing and loopback purposes.
Why A: Inside local is the private IP address assigned to a host inside the internal network. Inside global is the public IP address that represents that internal host to external networks. Static NAT creates a permanent one-to-one mapping between an inside local and an inside global address. PAT (Port Address Translation) extends NAT by using port numbers to map multiple inside local addresses to a single inside global address.
Last reviewed: Jun 6, 2026
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