Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A subnet requires 200 usable host addresses. Which prefix is the smallest that meets the requirement?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
/25
This is wrong because a /25 provides only 126 usable host addresses.
B
Best answer
/24
This is correct because a /24 provides 254 usable host addresses.
C
Distractor review
/26
This is wrong because a /26 provides only 62 usable host addresses.
D
Distractor review
/27
This is wrong because a /27 provides only 30 usable host addresses.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming the total number of IP addresses in a subnet equals the number of usable hosts. Candidates often select a /25 because it has 128 addresses, mistakenly thinking it covers 200 hosts. However, two addresses are reserved for network and broadcast, leaving only 126 usable hosts. This subtle difference causes many to pick an insufficient subnet size, leading to network issues or exam errors. Always subtract 2 from the total addresses to find usable hosts when choosing a subnet prefix.
Technical deep dive
How to think about this question
Subnetting is a fundamental concept in IP networking that divides a larger network into smaller, manageable segments called subnets. Each subnet has a defined prefix length, which determines the number of available host addresses. The prefix length, expressed as a slash followed by a number (e.g., /24), indicates how many bits are used for the network portion of the address, with the remaining bits used for host addressing. To determine the smallest prefix that meets a host requirement, you calculate the number of usable host addresses per subnet. The formula for usable hosts is 2^(32 - prefix) - 2, accounting for the network and broadcast addresses that cannot be assigned to hosts. For 200 usable hosts, a /24 prefix provides 254 usable addresses, which is the smallest prefix that satisfies this need. Smaller prefixes like /25 or /26 do not provide enough usable hosts. A common exam trap is confusing total addresses with usable host addresses. For example, a /25 subnet has 128 total addresses but only 126 usable hosts because two addresses are reserved. Misinterpreting this can lead to selecting an incorrect subnet size. In practical Cisco networking, correctly calculating subnet sizes ensures efficient IP address allocation and avoids address exhaustion or waste in network design.
KKey Concepts to Remember
- Subnetting divides an IP network into smaller subnets by allocating bits to the network and host portions of the address.
- The prefix length determines the number of bits used for the network, directly impacting the number of usable host addresses.
- Usable host addresses per subnet equal 2^(32 - prefix length) minus 2, accounting for network and broadcast addresses.
- A /24 subnet provides 254 usable host addresses, making it suitable for subnets requiring up to 254 hosts.
- Choosing a subnet prefix must ensure the number of usable hosts meets or exceeds the required host count to avoid address shortages.
- Network and broadcast addresses are reserved and cannot be assigned to hosts, reducing the total usable addresses by two.
- Misinterpreting total addresses as usable hosts is a common exam trap that leads to selecting an incorrect subnet size.
- Efficient subnetting in Cisco networks prevents IP address waste and supports scalable network design.
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.
Related practice questions
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
Subnetting divides an IP network into smaller subnets by allocating bits to the network and host portions of the address.
What is the correct answer to this question?
The correct answer is: /24 — A /24 is the smallest valid choice. In plain language, the subnet needs enough total addresses so that after the network and broadcast addresses are reserved, 200 hosts still remain. A /25 is too small because it provides only 126 usable hosts. A /24 provides 254 usable hosts, which satisfies the requirement while being the next logical prefix size up. This is a standard host-capacity planning question. The key is to work from usable hosts, not just total addresses, and then choose the smallest prefix that actually works.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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