CCNA Network Services and Security Practice Question
Which NAT design is most appropriate when many inside users need outbound Internet access through one public IPv4 address, but no inbound server publishing is required?
⚠ Common exam trap
A frequent exam trap is selecting static NAT or no NAT for outbound Internet access when many internal users share one public IP. Static NAT creates one-to-one mappings, consuming excessive public IP addresses unnecessarily. Choosing no NAT assumes private IPv4 addresses are routable on the Internet, which is false. Another trap is confusing DHCP relay with NAT; DHCP relay only forwards DHCP messages and does not perform address translation. Candidates must recognize that PAT overload is the correct design for many-to-one outbound translation without inbound server publishing, avoiding these common misconceptions.
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
✓
PAT overload
The most appropriate design is PAT overload. In practical terms, many internal users can share one public IPv4 address because PAT distinguishes their sessions using transport-layer ports. This is the most common solution when the requirement is outbound access for many clients rather than predictable inbound access to a specific internal server. Static NAT would be the wrong design here because it creates fixed one-to-one mappings and consumes more public address space than needed for this use case. PAT is specifically built for many-to-one outbound translation.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
PAT overload
Why this is correct
PAT overload (Port Address Translation) is the correct choice because it allows many internal devices to share a single public IPv4 address by multiplexing sessions based on transport-layer port numbers. Each inside host's traffic is assigned a unique source port, enabling thousands of concurrent outbound connections from a single public IP. This conserves the limited public IPv4 address space and is the standard solution for providing Internet access to a large user population.
- ✗
Static NAT for every host
Why it's wrong here
Static NAT for every host is incorrect because it requires a dedicated public IP address for each internal host, creating a one-to-one mapping. When many users need outbound Internet access, this approach exhausts public address space quickly and is operationally cumbersome to maintain. Static NAT is intended for servers that must be reachable from the outside, not for scaling outbound access for a large user base.
When this WOULD be correct
In a scenario where a network requires consistent inbound access to specific services hosted on internal servers, such as a web server or mail server, using Static NAT for those specific hosts would be appropriate to ensure that they are always reachable via the same public IP address.
- ✗
No NAT, because private IPv4 addresses are Internet-routable
Why it's wrong here
The claim that no NAT is needed because private IPv4 addresses are Internet-routable is false. Addresses defined in RFC 1918—such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16—are explicitly reserved for private use and are not routed on the public internet; ISP routers discard packets with these source addresses. Therefore, NAT is mandatory to translate private source addresses into a globally routable public IP before traffic leaves the internal network.
When this WOULD be correct
If the exam question stated that the network was using a new protocol or technology that allows private IPv4 addresses to be routable on the Internet, then 'No NAT' could be a correct answer. For example, if the question involved a scenario where IPv6 was implemented, making private IPv4 addresses routable would be valid.
- ✗
DHCP relay
Why it's wrong here
DHCP relay is not a NAT solution; it is a Layer 3 feature that forwards DHCP broadcast messages between a client and a DHCP server located on a different subnet. While DHCP assigns private IP addresses dynamically, it does nothing to translate those addresses for Internet communication. Without address translation, the private addresses remain non-routable on the Internet, so DHCP relay cannot satisfy the requirement of allowing many inside users to access the Internet.
When this WOULD be correct
If the question asked about a scenario where a network has multiple subnets and requires dynamic IP address assignment from a remote DHCP server, then DHCP relay would be the correct answer. This would involve forwarding DHCP packets across different network segments.
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.
✓PAT overloadCorrect answer▾
Why this is correct
PAT overload (Port Address Translation) is the correct choice because it allows many internal devices to share a single public IPv4 address by multiplexing sessions based on transport-layer port numbers. Each inside host's traffic is assigned a unique source port, enabling thousands of concurrent outbound connections from a single public IP. This conserves the limited public IPv4 address space and is the standard solution for providing Internet access to a large user population.
✗Static NAT for every hostWrong answer — click to see why▾
Why this is wrong here
Static NAT for every host is inefficient for scenarios with many internal users needing outbound access, as it requires a unique public IP for each private IP, leading to a scarcity of public addresses and increased management overhead.
★ When this WOULD be the correct answer
In a scenario where a network requires consistent inbound access to specific services hosted on internal servers, such as a web server or mail server, using Static NAT for those specific hosts would be appropriate to ensure that they are always reachable via the same public IP address.
Why candidates choose this
Candidates might choose this option because they recall that Static NAT provides a direct mapping between private and public IPs, which can seem appealing for ensuring reliable communication, even though it doesn't fit the question's requirements.
✗No NAT, because private IPv4 addresses are Internet-routableWrong answer — click to see why▾
Why this is wrong here
This option is wrong because private IPv4 addresses are not routable on the Internet; they cannot be used for outbound access without NAT. Therefore, using no NAT would prevent internal users from accessing the Internet.
★ When this WOULD be the correct answer
If the exam question stated that the network was using a new protocol or technology that allows private IPv4 addresses to be routable on the Internet, then 'No NAT' could be a correct answer. For example, if the question involved a scenario where IPv6 was implemented, making private IPv4 addresses routable would be valid.
Why candidates choose this
Candidates may choose this option due to a misunderstanding of NAT concepts, believing that private addresses can be used directly on the Internet without realizing the necessity of NAT for outbound connectivity.
✗DHCP relayWrong answer — click to see why▾
Why this is wrong here
DHCP relay is not relevant to NAT design; it is used to forward DHCP requests from clients to a DHCP server located on a different network. This option does not address the need for outbound Internet access through a single public IP address.
★ When this WOULD be the correct answer
If the question asked about a scenario where a network has multiple subnets and requires dynamic IP address assignment from a remote DHCP server, then DHCP relay would be the correct answer. This would involve forwarding DHCP packets across different network segments.
Why candidates choose this
Candidates may confuse DHCP relay with NAT functions, thinking that it relates to managing IP addresses for Internet access, leading them to select it despite it not addressing the specific requirements of the question.
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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Key term
NAT
NAT (Network Address Translation) is a method that allows multiple devices on a private network to share a single public IP address when accessing the internet.
Key term
Static NAT
Static Network Address Translation (NAT) is a one-to-one mapping between a private IP address and a public IP address that never changes.
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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.