The answer is the ability to access the internet. Without a default gateway, a computer can still communicate with other devices on the same local LAN because it uses ARP to resolve local IP addresses directly, but it cannot route traffic to external networks. The default gateway acts as the exit point for any packet destined outside the local subnet, so when it is missing, the computer has no way to reach the internet or any other remote network. On the CompTIA A+ Core 1 220-1201 exam, this concept tests your understanding of basic IP configuration and routing; a common trap is assuming all communication fails, but local traffic remains unaffected. A helpful memory tip is to think of the default gateway as the “door to the outside world”—without it, you can still talk to your neighbors, but you cannot leave the neighborhood.
220-1101 Network Configuration Concepts Practice Question
This 220-1201 practice question tests your understanding of network configuration concepts. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 technician is configuring a small network with five computers and a printer. The network must use private IP addresses and allow all devices to communicate. The technician assigns IPs manually but forgets to set a default gateway on one computer. Which functionality will be lost on that computer?
Why wrong: The printer is on the same subnet, so communication is possible without a default gateway using ARP and direct MAC addressing.
B
Ability to access the internet
Without a default gateway, the computer cannot send packets to destinations outside its own subnet, so internet access is lost.
C
Ability to obtain an IP address via DHCP
Why wrong: The IP is assigned manually, so DHCP is not used; the default gateway is irrelevant to IP assignment.
D
Ability to resolve DNS names
Why wrong: DNS resolution may still work if the DNS server is on the same subnet, but typically DNS servers are external; however, the primary loss is internet routing.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Ability to access the internet
The default gateway is required for routing traffic to other networks, such as the internet. Without it, the computer can still communicate with devices on the same subnet (local LAN) but cannot reach external networks.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Ability to communicate with the printer
Why it's wrong here
The printer is on the same subnet, so communication is possible without a default gateway using ARP and direct MAC addressing.
✓
Ability to access the internet
Why this is correct
Without a default gateway, the computer cannot send packets to destinations outside its own subnet, so internet access is lost.
The IP is assigned manually, so DHCP is not used; the default gateway is irrelevant to IP assignment.
✗
Ability to resolve DNS names
Why it's wrong here
DNS resolution may still work if the DNS server is on the same subnet, but typically DNS servers are external; however, the primary loss is internet routing.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 220-1201 question in full detail.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 220-1201 subnetting questions on CIDR, address ranges, and subnet selection.
Network Configuration Concepts — This question tests Network Configuration Concepts — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Ability to access the internet — The default gateway is required for routing traffic to other networks, such as the internet. Without it, the computer can still communicate with devices on the same subnet (local LAN) but cannot reach external networks.
What should I do if I get this 220-1201 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 220-1201 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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