- A
DHCP
Why wrong: DHCP assigns IP addresses to internal devices, but it does not translate those addresses for internet access.
- B
DNS
Why wrong: DNS resolves domain names to IP addresses, but it does not enable multiple devices to share a single public IP.
- C
NAT
NAT translates private internal IP addresses to the router's public IP, allowing multiple devices to share the internet connection.
- D
PAT
Why wrong: PAT is a specific type of NAT that uses port numbers, but the general service required is NAT.
Question 123 of 1,020
NAT: Enable Internet Sharing for Multiple Devices
This 220-1201 practice question tests your understanding of network services. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.
A small office has a single internet connection and needs to allow multiple internal devices to share that connection. The router's public IP is assigned by the ISP. Which network service must be enabled on the router to allow internal devices to communicate with external servers?
Quick Answer
The answer is Network Address Translation (NAT), because it enables internet sharing for multiple devices on a private network by translating their internal private IP addresses into the single public IP assigned by the ISP. This process allows all internal devices to communicate with external servers through one connection, effectively conserving public IP addresses while providing internet access. On the CompTIA A+ Core 1 220-1201 exam, this concept tests your understanding of how a router bridges private and public networks; a common trap is confusing NAT with DHCP, which only assigns internal IPs and does not enable internet sharing, or with PAT, which is a specific form of NAT rather than the broad service. Remember the memory tip: NAT is the “bouncer” that lets your whole party (multiple devices) use one VIP pass (the public IP) to get into the club (the internet).
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
✓
NAT
NAT (Network Address Translation) is required because it allows multiple internal devices with private IP addresses to share a single public IP address assigned by the ISP. When internal devices send traffic to external servers, NAT translates the private source IP and port to the router's public IP and a unique port, enabling responses to return to the correct internal host. Without NAT, the router would drop packets from private addresses destined for the internet, as they are not routable on the public internet.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
DHCP
Why it's wrong here
DHCP assigns IP addresses to internal devices, but it does not translate those addresses for internet access.
- ✗
DNS
Why it's wrong here
DNS resolves domain names to IP addresses, but it does not enable multiple devices to share a single public IP.
- ✓
NAT
Why this is correct
NAT translates private internal IP addresses to the router's public IP, allowing multiple devices to share the internet connection.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
PAT
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often mistakenly choose PAT because they think it is the only method for sharing a single IP, but the question asks for the general service (NAT) that enables multiple devices to share a connection, and PAT is just a subset of NAT.
Detailed technical explanation
How to think about this question
NAT operates by maintaining a translation table in the router's memory, mapping each internal private IP and port to the router's public IP and a dynamically assigned port (often in the range 1024–65535). When a response packet arrives, the router looks up the destination port in the table to reverse-translate the address back to the correct internal host. In real-world scenarios, NAT can cause issues with protocols that embed IP addresses in the payload (e.g., FTP, SIP), requiring Application Layer Gateway (ALG) support to rewrite those fields.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this 220-1201 question test?
Network Services — This question tests Network Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: NAT — NAT (Network Address Translation) is required because it allows multiple internal devices with private IP addresses to share a single public IP address assigned by the ISP. When internal devices send traffic to external servers, NAT translates the private source IP and port to the router's public IP and a unique port, enabling responses to return to the correct internal host. Without NAT, the router would drop packets from private addresses destined for the internet, as they are not routable on the public internet.
What should I do if I get this 220-1201 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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