CCNA Network Services and Security Practice Question
Exhibit
`ip nat inside source list 1 interface GigabitEthernet0/1 overload`
A router is configured for PAT using the WAN interface address. Which command element is most directly associated with allowing many internal users to share that single outside address?
⚠ Common exam trap
A common exam trap is selecting options like `inside`, `list 1`, or `interface` as the element that enables multiple internal users to share a single outside address. While these elements are part of the NAT configuration, they do not by themselves enable PAT. The `inside` keyword only marks interfaces as internal, the ACL (`list 1`) defines which addresses are translated, and specifying the `interface` chooses the public IP address source. However, without the `overload` keyword, the router cannot perform port-based multiplexing, so many-to-one sharing fails. Candidates often overlook that `overload` is the explicit command that activates PAT, making it the correct answer.
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
✓
overload
The `overload` element is the critical part. In plain language, that keyword tells the router to perform Port Address Translation so many inside sessions can be represented through the same outside IP address at the same time. Without overload, the router would be performing a different translation behavior and would not achieve the same many-to-one sharing model. This is one of the most recognizable NAT design terms in CCNA because it directly distinguishes PAT from simple one-to-one translation methods. The correct answer is the part of the configuration that signals multi-session sharing through port tracking.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
overload
Why this is correct
The `overload` keyword is the essential PAT enabler in an `ip nat inside source list ... interface ... overload` command. Without it, the router performs only dynamic NAT, mapping one inside local address to one inside global address at a time. Overload forces the router to reuse the single WAN interface IP address by multiplexing sessions through unique transport-layer port numbers, supporting many inside hosts simultaneously. This keyword directly translates to Port Address Translation, making it the correct answer.
- ✗
inside
Why it's wrong here
The `inside` keyword appears in the command's beginning (`ip nat inside ...`) to specify the direction of translation, marking the internal network side of the NAT boundary. It is necessary to define which interfaces are considered inside, but it does not enable many-to-one sharing of a single public address. Even if `inside` is present, PAT behavior requires `overload` to allow multiple internal users to share the WAN interface address. Thus, `inside` alone is insufficient for the described PAT requirement.
When this WOULD be correct
In a different question asking about identifying the internal network designation in a NAT configuration, the option 'inside' would be correct when the question specifies which command element defines the internal IP address range used for NAT translations.
- ✗
list 1
Why it's wrong here
The `list 1` parameter refers to a standard access control list (e.g., `access-list 1 permit ...`) that identifies which internal source addresses are eligible for translation. It selects traffic that will be NATed but does not determine how addresses are translated or whether port multiplexing is used. Without `overload`, an ACL simply defines a pool of candidates for one-to-one dynamic NAT, which would exhaust public IPs. Therefore `list 1` plays a supporting role, not the PAT-enabling role, making it incorrect.
When this WOULD be correct
In a different question that asks about the purpose of access lists in NAT configurations, 'list 1' could be the correct answer if the question specifies that it is used to permit or deny specific internal addresses from being translated to the outside address.
- ✗
interface
Why it's wrong here
The `interface` keyword specifies the source of the inside global address—in this case, the WAN interface's IP address—as the public address to be used in translated packets. It defines *where* the shared public IP comes from, but does not by itself implement many-to-one translation. A router could use `interface` without `overload`, resulting in dynamic NAT that only translates as many sessions as available addresses (which is just one for a single interface IP), dropping or failing additional connections. Only adding `overload` converts this to PAT, making `interface` an incomplete answer.
When this WOULD be correct
In a different question, if it asked about the command used to specify which interface to apply PAT on, 'interface' would be correct. For example, a question could ask, 'Which command element is used to define the external interface for NAT?'
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.
✓overloadCorrect answer▾
Why this is correct
The `overload` keyword is the essential PAT enabler in an `ip nat inside source list ... interface ... overload` command. Without it, the router performs only dynamic NAT, mapping one inside local address to one inside global address at a time. Overload forces the router to reuse the single WAN interface IP address by multiplexing sessions through unique transport-layer port numbers, supporting many inside hosts simultaneously. This keyword directly translates to Port Address Translation, making it the correct answer.
✗insideWrong answer — click to see why▾
Why this is wrong here
The 'inside' command element specifies the internal network from which traffic originates but does not directly facilitate the sharing of a single external address among multiple users. It is not responsible for the overload feature that enables PAT.
★ When this WOULD be the correct answer
In a different question asking about identifying the internal network designation in a NAT configuration, the option 'inside' would be correct when the question specifies which command element defines the internal IP address range used for NAT translations.
Why candidates choose this
Candidates may confuse the term 'inside' with the concept of internal users, leading them to believe it plays a crucial role in the context of sharing an external address, despite its actual function being more about defining the internal network.
✗list 1Wrong answer — click to see why▾
Why this is wrong here
The command element 'list 1' refers to an access list that defines which internal IP addresses can be translated. While it is necessary for configuring PAT, it does not directly enable multiple users to share a single outside address, which is the focus of the question.
★ When this WOULD be the correct answer
In a different question that asks about the purpose of access lists in NAT configurations, 'list 1' could be the correct answer if the question specifies that it is used to permit or deny specific internal addresses from being translated to the outside address.
Why candidates choose this
Candidates may choose 'list 1' because they associate access lists with NAT configurations and believe that controlling which addresses can be translated is directly related to sharing an outside address.
✗interfaceWrong answer — click to see why▾
Why this is wrong here
The 'interface' command element specifies the WAN interface used for PAT but does not directly enable multiple internal users to share a single outside address. It is part of the configuration but does not perform the function of overload.
★ When this WOULD be the correct answer
In a different question, if it asked about the command used to specify which interface to apply PAT on, 'interface' would be correct. For example, a question could ask, 'Which command element is used to define the external interface for NAT?'
Why candidates choose this
Candidates may choose 'interface' because they associate it with the configuration of NAT and might mistakenly believe it directly relates to the functionality of allowing multiple users to share an address, overlooking the specific role of 'overload' in this context.
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?”
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.