easyMultiple ChoiceObjective-mapped
220-1201 Practice Question: A small office has a single internet connection…
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?
⚠ Common exam trap
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.
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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DHCP
Why it's wrong here
DHCP (Dynamic Host Configuration Protocol) is responsible for automatically assigning IP addresses, subnet masks, default gateways, and DNS server information to devices within a local area network. While essential for internal network configuration and device communication, DHCP does not perform any address translation or routing functions that would allow multiple devices with private IP addresses to share a single public IP address for internet access. Its role is purely for internal network setup, not for external internet sharing.
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DNS
Why it's wrong here
DNS (Domain Name System) provides the critical service of translating human-readable domain names, such as 'example.com', into numerical IP addresses that computers use to locate resources on the internet. Although fundamental for web browsing and internet navigation, DNS operates at the application layer and does not facilitate the sharing of a single public IP address among multiple internal devices. It merely resolves names to addresses, rather than enabling the necessary address translation or multiplexing for shared internet connectivity.
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NAT
Why this is correct
NAT (Network Address Translation) is a fundamental networking service that modifies the network address information in the IP header of packets as they traverse a router. It specifically translates private, non-routable IP addresses used within a local network into a single, routable public IP address assigned to the router's external interface. This process enables multiple devices on a private network to simultaneously share one public IP address for outbound internet access, conserving public IPv4 addresses and enhancing security by obscuring the internal network topology.
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PAT
Why it's wrong here
PAT (Port Address Translation), also known as NAT Overload or NAPT (Network Address Port Translation), is a specific and widely used form of NAT. It allows many internal private IP addresses to share a single public IP address by assigning different source port numbers to each outgoing connection. While PAT is the practical implementation of NAT commonly found in small office/home office routers to enable internet sharing, the overarching concept and the general service that translates private IPs to a public IP for shared internet access is NAT itself, making NAT the more encompassing and correct answer for the fundamental requirement.
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Related to this question
Learn chapter
Network Configuration: IP, DNS, DHCP
Key term
IP address
An IP address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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