Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A host address is 172.31.9.200/27. Which address is the first usable host in that 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
172.31.9.193
This is correct because 172.31.9.192 is the network address and .193 is the first usable host.
B
Distractor review
172.31.9.192
This is wrong because .192 is the network address of the subnet.
C
Distractor review
172.31.9.223
This is wrong because .223 is the broadcast address of the subnet.
D
Distractor review
172.31.9.201
This is wrong because .201 is usable, but not the first usable host.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting the network address (172.31.9.192) as the first usable host. This mistake arises because the network address is the base of the subnet block but is reserved and cannot be assigned to a host. Another trap is confusing the broadcast address (172.31.9.223) with a usable host, which is invalid since the broadcast address is reserved for network-wide communication. Candidates must carefully calculate the subnet range and remember that the first usable host is always the network address plus one.
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 subnetworks. A /27 subnet mask corresponds to 255.255.255.224, which means 27 bits are used for the network portion and 5 bits for host addresses. This results in 32 IP addresses per subnet block, including network and broadcast addresses, leaving 30 usable host addresses. The block size of 32 is derived from the last octet's subnet mask bits, which define the range of IP addresses within each subnet. To determine the first usable host address in a /27 subnet, you first identify the network address by zeroing out the host bits. For the IP 172.31.9.200/27, the subnet block containing 200 is 192-223. The network address is 172.31.9.192, and the broadcast address is 172.31.9.223. The first usable host is the network address plus one, which is 172.31.9.193. This process is essential for correctly assigning IP addresses and avoiding conflicts in Cisco networks. A common exam trap is confusing the network address with the first usable host address. Candidates often mistake the network address (172.31.9.192) as a valid host IP, which it is not. Understanding the role of network and broadcast addresses in subnetting helps avoid this error. Practically, Cisco devices use this logic to route traffic correctly and prevent IP conflicts, making precise subnet calculations critical for network design and troubleshooting.
KKey Concepts to Remember
- A /27 subnet mask divides the IP address space into blocks of 32 addresses, including network and broadcast addresses.
- The network address is the lowest IP in the subnet block and cannot be assigned to a host device.
- The first usable host address is always the network address plus one within the subnet range.
- The broadcast address is the highest IP in the subnet block and is reserved for network-wide communication.
- Subnetting requires calculating the block size to determine valid network, broadcast, and host addresses.
- Cisco devices use subnetting rules to route traffic correctly and prevent IP address conflicts.
- Confusing the network or broadcast address as usable hosts is a common subnetting mistake in Cisco exams.
- Understanding subnetting fundamentals is critical for IP address planning and troubleshooting in Cisco networks.
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?
A /27 subnet mask divides the IP address space into blocks of 32 addresses, including network and broadcast addresses.
What is the correct answer to this question?
The correct answer is: 172.31.9.193 — A /27 subnet has a block size of 32. In practical terms, the relevant last-octet blocks are 0-31, 32-63, 64-95, 96-127, 128-159, 160-191, 192-223, and 224-255. Because 200 falls within the 192-223 block, the network address is 172.31.9.192 and the first usable host is 172.31.9.193. This is a host-range interpretation problem rather than just network-or-broadcast recognition.
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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