220-1101 Networking Practice Question
A network technician is setting up a small office with 15 workstations. The ISP provides a single public IPv4 address. The technician configures the router to assign private IP addresses (192.168.1.x) to the workstations via DHCP. Which technology allows all 15 workstations to share the single public IP address to access the internet?
⚠ Common exam trap
Candidates often confuse DHCP (which assigns private IPs) with the technology that actually enables internet access through a single public IP, mistakenly thinking DHCP alone provides internet connectivity.
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 (Network Address Translation)
NAT (Network Address Translation) allows multiple devices on a private network (like 192.168.1.x) to share a single public IPv4 address by translating the private source IP and port to the public IP and a unique port number when traffic exits the router. This enables all 15 workstations to access the internet simultaneously using the one public address provided by the ISP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
NAT (Network Address Translation)
Why this is correct
NAT (specifically PAT/NAPT) maps multiple private RFC 1918 addresses to a single public IP assigned by the ISP, using a dynamic translation table keyed by IP and TCP/UDP port. Each of the 15 devices sends traffic with its private address, and the router rewrites the source to the public IP, remembering which internal device owns each session. When replies arrive, the router consults the table and forwards them to the correct private IP. This is exactly how a small office shares one internet connection.
- ✗
DNS (Domain Name System)
Why it's wrong here
DNS translates human-readable domain names into IPv4 or IPv6 addresses, but it never modifies IP headers or rewrites addressing. It is a global directory service that resolves names to the public IP of a server, not a mechanism for many clients to share one public IP. Even with DNS properly configured on every device, the clients still need routable addresses themselves, so it cannot provide the required internet sharing for 15 devices.
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DHCP (Dynamic Host Configuration Protocol)
Why it's wrong here
DHCP dynamically assigns IP addresses, subnet masks, default gateways, and DNS server settings to clients from a configured address pool. It streamlines network configuration by leasing private addresses to the 15 workstations, but those addresses are non-routable on the internet. DHCP does not perform any translation or rewriting of packet headers, so without a NAT gateway, the leased private addresses cannot reach the internet through a single public IP.
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ARP (Address Resolution Protocol)
Why it's wrong here
ARP maps a known IPv4 address to a physical MAC address on a local network segment, sending broadcast requests to find which host owns an IP. It operates entirely within Layer 2 and a single subnet, maintaining an ARP cache that is meaningless outside that broadcast domain. ARP has no concept of public versus private addressing and cannot translate or multiplex multiple internal addresses onto one external IP.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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