Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A subnet must support 14 usable hosts. 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
/29
This is wrong because a /29 provides only 6 usable host addresses.
B
Best answer
/28
This is correct because a /28 provides 16 total addresses and 14 usable hosts.
C
Distractor review
/27
This is wrong because /27 would work, but it is larger than necessary.
D
Distractor review
/26
This is wrong because /26 provides far more host addresses than needed.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is mistaking the total number of IP addresses in a subnet for the number of usable host addresses. Candidates often select a /29 subnet because it has 8 total addresses, mistakenly assuming all are usable. However, two addresses are reserved for network and broadcast, leaving only 6 usable hosts, which is insufficient for 14 hosts. Another trap is choosing a /27 or /26 subnet, which supports more hosts than necessary, wasting IP addresses and potentially confusing subnet calculations. Understanding the difference between total and usable addresses is critical to avoid these pitfalls.
Technical deep dive
How to think about this question
Subnetting is the process of dividing a larger IP network into smaller, more manageable subnetworks, each with its own range of IP addresses. The subnet mask or prefix length determines how many bits are used for the network portion versus the host portion of the address. In IPv4, the number of host bits directly affects how many usable host addresses a subnet can support, since two addresses are reserved: one for the network identifier and one for the broadcast address. To determine the smallest subnet prefix that supports 14 usable hosts, you calculate the total number of addresses needed by adding 2 reserved addresses to the required hosts, resulting in 16 total addresses. A /28 prefix corresponds to 32 - 28 = 4 host bits, which yields 2^4 = 16 total addresses. This perfectly fits the requirement, providing exactly 14 usable host addresses. Prefixes longer than /28 (like /29) provide fewer host addresses, while shorter prefixes (like /27 or /26) provide more than necessary, leading to inefficient IP address utilization. A common exam trap is to confuse total addresses with usable hosts, leading to selecting a subnet that is too small or unnecessarily large. For example, a /29 subnet provides 8 total addresses but only 6 usable hosts, which is insufficient for 14 hosts. Conversely, choosing a /27 or /26 subnet wastes IP addresses by allocating more hosts than needed. In practical Cisco networking, efficient subnetting conserves IP space and simplifies network management, making /28 the optimal choice for exactly 14 hosts.
KKey Concepts to Remember
- Subnetting divides an IP network into smaller subnets by allocating bits between network and host portions of the address.
- The number of host bits in a subnet mask determines the total number of IP addresses available in that subnet.
- Two IP addresses in every subnet are reserved: one for the network address and one for the broadcast address, reducing usable hosts.
- A /28 subnet mask provides 16 total IP addresses, which equals 14 usable host addresses after reserving network and broadcast addresses.
- Choosing a subnet prefix that is too large wastes IP addresses and can lead to inefficient network design.
- Selecting a subnet prefix that is too small results in insufficient usable host addresses for the required hosts.
- Cisco networking best practices emphasize efficient subnetting to conserve IP address space and simplify network management.
- Understanding the difference between total addresses and usable hosts is essential to correctly determine subnet sizes on the CCNA exam.
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
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
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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 between network and host portions of the address.
What is the correct answer to this question?
The correct answer is: /28 — To support 14 usable hosts, the subnet must have 16 total addresses, because two are reserved for the network and broadcast addresses. In plain language, you need enough address slots so that after those two reserved entries are removed, 14 remain. A /28 provides exactly that: 16 total addresses and 14 usable addresses. This is a classic minimum-subnet-size question because it tests whether you can work backward from host requirement to prefix length. A /29 would be too small, while a /27 would work but waste more addresses than necessary.
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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