200-901 Network Fundamentals Practice Question
A network administrator notices that a host with IP 192.168.1.10/25 cannot communicate with a host at 192.168.1.200/25. What is the most likely reason?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The subnet mask is incorrect; they are on different subnets.
With a /25 mask (255.255.255.128), the network is divided into two subnets: 192.168.1.0-127 and 192.168.1.128-255. The two hosts are in different subnets and require a router to communicate.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The default gateway is missing.
Why it's wrong here
Even with a gateway, they are on different subnets; but the gateway could route, but the question asks most likely reason. Actually, both could be true, but the subnet mismatch is the root cause.
- ✓
The subnet mask is incorrect; they are on different subnets.
Why this is correct
192.168.1.10 is in subnet 0, 192.168.1.200 is in subnet 128.
- ✗
The ARP cache is corrupted.
Why it's wrong here
ARP is needed for same subnet; they are on different subnets.
- ✗
The hosts are using different DNS servers.
Why it's wrong here
DNS is not involved in local communication.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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