Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A host is configured with 10.10.10.130/25. What is the network address of its 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
Distractor review
10.10.10.0
This is wrong because .130 is not in the lower 0–127 /25 block.
B
Distractor review
10.10.10.64
This is wrong because /25 does not create boundaries at 64.
C
Best answer
10.10.10.128
This is correct because .130 falls in the upper /25 block starting at .128.
D
Distractor review
10.10.10.255
This is wrong because .255 is the broadcast address of that /25, not the network address.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is mistaking the broadcast address or a lower subnet block as the network address. Candidates often see 10.10.10.255 and assume it is the network address, but it is actually the broadcast address for the 10.10.10.128/25 subnet. Another pitfall is assuming the subnet boundary falls at 64, confusing /25 with smaller subnet masks like /26 or /27. This leads to selecting 10.10.10.64 incorrectly. The key is to recognize that /25 splits the address space exactly in half at 128, not at 64 or 0.
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. The subnet mask determines how the IP address is split between the network and host portions. In this question, the /25 mask means the first 25 bits represent the network portion, leaving 7 bits for host addresses. This creates two equal-sized subnets within the original Class C range, each with 128 addresses. The /25 subnet mask (255.255.255.128) splits the 10.10.10.0 network into two subnets: 10.10.10.0/25 and 10.10.10.128/25. The first subnet covers IP addresses from 10.10.10.0 to 10.10.10.127, and the second subnet covers 10.10.10.128 to 10.10.10.255. Since the host IP is 10.10.10.130, it falls within the second subnet range, making 10.10.10.128 the correct network address. A common exam trap is confusing the subnet boundaries or misinterpreting the broadcast address as the network address. For example, 10.10.10.255 is the broadcast address for the 10.10.10.128/25 subnet, not the network address. Understanding how subnet masks define network and broadcast addresses helps avoid this mistake and ensures accurate subnet identification in Cisco networking scenarios.
KKey Concepts to Remember
- A /25 subnet mask divides a Class C network into two subnets, each containing 128 IP addresses.
- The network address is the first IP in the subnet range and is always a multiple of the subnet size, here 128.
- The host IP 10.10.10.130 falls within the 10.10.10.128/25 subnet because it is between 128 and 255.
- The broadcast address is the last IP in the subnet range and cannot be used as a network address.
- Subnetting requires understanding how subnet masks define network and host portions of an IP address.
- Cisco devices use subnet masks to determine if a destination IP is local or requires routing.
- Misidentifying subnet boundaries leads to incorrect network address selection and routing errors.
- Accurate subnetting skills are essential for configuring VLANs, ACLs, and routing protocols 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 /25 subnet mask divides a Class C network into two subnets, each containing 128 IP addresses.
What is the correct answer to this question?
The correct answer is: 10.10.10.128 — A /25 divides the address space into two blocks of 128 addresses. In plain language, the ranges are 0–127 and 128–255. Since the host ends in 130, it belongs to the 128–255 half. That means the network address is 10.10.10.128. This is a common subnet-boundary question because it tests whether you can map a host address into the correct prefix block quickly and confidently.
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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