Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A host is configured with IP address 192.168.70.18/30. Which addresses belong to the same subnet block?
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
192.168.70.16 through 192.168.70.19
This is correct because .18 belongs to the /30 block that runs from .16 to .19.
B
Distractor review
192.168.70.18 through 192.168.70.21
This is wrong because /30 block boundaries do not start at .18.
C
Distractor review
192.168.70.12 through 192.168.70.15
This is wrong because that is the previous /30 block.
D
Distractor review
192.168.70.20 through 192.168.70.23
This is wrong because that is the next /30 block.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming that the subnet block starts at the host IP address rather than the correct subnet boundary. For example, selecting the range 192.168.70.18 through 192.168.70.21 seems logical because it includes the host IP, but it ignores that /30 subnets are aligned on multiples of 4. This mistake overlooks that the subnet block must start at 192.168.70.16, the nearest multiple of 4 less than or equal to 18. Misunderstanding subnet boundaries leads to incorrect network and broadcast addresses, which can cause routing and communication failures in real networks and incorrect answers on the exam.
Technical deep dive
How to think about this question
Subnetting is a fundamental concept in IP networking that divides a larger network into smaller subnetworks, or subnets, to improve routing efficiency and enhance security. A subnet mask determines the size of each subnet by specifying which portion of the IP address represents the network and which represents the host. In this question, the IP address 192.168.70.18/30 uses a subnet mask of 255.255.255.252, which means the last 2 bits of the host portion are used for host addresses, allowing for 4 IP addresses per subnet block. The /30 subnet mask creates subnet blocks with a block size of 4 addresses, calculated as 2^(32-30) = 4. These blocks start at multiples of 4 in the last octet, such as 0, 4, 8, 12, 16, 20, and so forth. Each block includes one network address, two usable host addresses, and one broadcast address. Since 192.168.70.18 falls within the 16–19 range, the subnet block includes 192.168.70.16 (network), 192.168.70.17 and 192.168.70.18 (usable hosts), and 192.168.70.19 (broadcast). A common exam trap is confusing the subnet boundaries or assuming the subnet starts at the host IP itself rather than the nearest multiple of the block size. This leads to incorrect subnet ranges such as 18–21 or 20–23. In practical Cisco networking, understanding subnet boundaries is crucial for configuring interfaces, ACLs, and routing protocols correctly, as misidentifying subnet ranges can cause connectivity issues or routing failures.
KKey Concepts to Remember
- A /30 subnet mask creates subnet blocks of 4 IP addresses, including network, usable hosts, and broadcast addresses.
- Subnet boundaries align with multiples of the block size, which is calculated as 2^(32 - subnet mask prefix).
- The network address is the first IP in the subnet block and is not assignable to hosts.
- The broadcast address is the last IP in the subnet block and is used to send packets to all hosts in the subnet.
- Usable host addresses fall between the network and broadcast addresses and can be assigned to devices.
- Cisco devices use subnet masks to determine if an IP address is local or remote for routing decisions.
- Misidentifying subnet boundaries leads to incorrect network and broadcast addresses, causing connectivity issues.
- Understanding subnetting is essential for configuring interfaces, ACLs, and routing protocols correctly 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.
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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 /30 subnet mask creates subnet blocks of 4 IP addresses, including network, usable hosts, and broadcast addresses.
What is the correct answer to this question?
The correct answer is: 192.168.70.16 through 192.168.70.19 — A /30 subnet has a block size of 4. In practical terms, the relevant blocks in the last octet are 0–3, 4–7, 8–11, 12–15, 16–19, and so on. Because 18 falls inside the 16–19 block, the subnet includes network address .16, usable hosts .17 and .18, and broadcast .19. This question checks whether you can identify the correct /30 block and understand all addresses that fall inside it.
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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