hardMultiple ChoiceObjective-mapped
220-1201 Practice Question: A technician is configuring a new router for a…
A technician is configuring a new router for a branch office. The ISP provides a public IP of 203.0.113.10/30 for the WAN interface. How many usable IP addresses does the technician have for devices on the WAN link?
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
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2
A /30 subnet mask (255.255.255.252) provides 4 total addresses: one network, one broadcast, and two usable. This is commonly used for point-to-point WAN links to conserve public IPs.
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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2
Why this is correct
This is the correct answer. A /30 subnet mask, which is 255.255.255.252, reserves 30 bits for the network portion. This leaves 2 bits for host addresses, resulting in 2^2 = 4 total IP addresses. From these 4 addresses, one is designated as the network address and another as the broadcast address, leaving exactly two usable IP addresses for host devices, such as the two endpoints of a point-to-point router connection.
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4
Why it's wrong here
This option is incorrect because while a /30 subnet does encompass a total of four IP addresses (2^2 host bits), it does not provide four usable addresses for devices. The first address in any subnet is reserved as the network address, and the last address is reserved as the broadcast address. Therefore, two addresses are always unavailable for host assignment, leaving only two available for actual device configuration.
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6
Why it's wrong here
This option is incorrect. A /29 subnet mask (255.255.255.248) utilizes 29 bits for the network portion, leaving 3 bits for host addresses. This configuration yields 2^3 = 8 total IP addresses, from which two are reserved for the network and broadcast addresses, resulting in six usable host addresses. However, the question specifically refers to a /30 subnet, not a /29.
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1
Why it's wrong here
This option is incorrect. A /30 subnet is designed to provide two usable IP addresses, which is the minimum required for a point-to-point link between two devices like routers. Providing only one usable address would render the subnet impractical for any connection requiring two endpoints, as it would lack a second address for the other side of the link.
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Network Configuration: IP, DNS, DHCP
Key term
WAN
A Wide Area Network (WAN) is a telecommunications network that connects multiple smaller networks, like local area networks, across large geographical distances.
Key term
Subnet
A subnet is a logical subdivision of an IP network, created by partitioning a larger network address space using subnet masks.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 220-1201 practice question is part of Courseiva's free CompTIA 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 220-1201 exam.