Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A subnet uses the mask 255.255.255.252. How many usable host addresses are available in each subnet?
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
Best answer
2
This is correct because /30 provides 4 total addresses and 2 usable hosts.
B
Distractor review
4
This is wrong because that is the total number of addresses, not the usable host count.
C
Distractor review
6
This is wrong because /30 subnets do not provide 6 usable hosts.
D
Distractor review
14
This is wrong because 14 usable hosts corresponds to a /28 subnet.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is confusing the total number of IP addresses in a subnet with the number of usable host addresses. For a /30 subnet, there are 4 total addresses, but only 2 can be assigned to hosts because the first address is reserved as the network identifier and the last as the broadcast address. Selecting 4 as the number of usable hosts overlooks these reserved addresses and leads to incorrect answers. This mistake often occurs because candidates quickly associate the subnet mask with the total address count without applying the subtraction rule for network and broadcast addresses.
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. The subnet mask 255.255.255.252 corresponds to a /30 prefix length, which means the first 30 bits are fixed for the network portion, leaving only 2 bits for host addressing. This small subnet size is commonly used in point-to-point links where only two devices need to communicate directly. The calculation for usable hosts in a subnet follows the formula 2^n - 2, where n is the number of host bits. For a /30 mask, n equals 2, so 2^2 = 4 total addresses. Subtracting the network address and broadcast address leaves 2 usable host IP addresses. Cisco devices and CCNA exams expect candidates to recognize this pattern quickly, as /30 subnets are standard for efficient IP address allocation in WAN links. A common exam trap is confusing total addresses with usable host addresses. Candidates might see 4 total addresses and mistakenly select 4 as usable hosts, ignoring that the network and broadcast addresses cannot be assigned to hosts. Practically, this means that a /30 subnet is ideal for point-to-point links but unsuitable for larger LAN segments requiring more hosts.
KKey Concepts to Remember
- A subnet mask of 255.255.255.252 corresponds to a /30 prefix length in IPv4 addressing.
- A /30 subnet provides 4 total IP addresses, including network and broadcast addresses.
- Usable host addresses in a subnet are calculated by subtracting network and broadcast addresses from total addresses.
- The formula 2^n - 2 determines usable hosts, where n is the number of host bits in the subnet mask.
- In a /30 subnet, only 2 usable host addresses are available for device assignment.
- Cisco CCNA exams expect candidates to distinguish between total IP addresses and usable host addresses in subnetting questions.
- Point-to-point links commonly use /30 subnets to efficiently allocate IP addresses with minimal waste.
- Misinterpreting total addresses as usable hosts is a frequent exam trap in subnetting questions.
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?
A subnet mask of 255.255.255.252 corresponds to a /30 prefix length in IPv4 addressing.
What is the correct answer to this question?
The correct answer is: 2 — The mask 255.255.255.252 corresponds to /30. In practical terms, that gives 4 total addresses per subnet. After subtracting the network and broadcast addresses, 2 usable host addresses remain. This is a classic small-subnet calculation that often appears in point-to-point addressing scenarios.
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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