hardMultiple Choice
FC0-U71 Practice Question: Refer to the exhibit
Exhibit
Router1 configuration: interface FastEthernet0/0 ip address 192.168.1.1 255.255.255.0 ip route 0.0.0.0 0.0.0.0 10.0.0.1 Switch1: VLAN1, IP 192.168.1.2/24 PC1: IP 192.168.1.10/24, gateway 192.168.1.1 PC2: IP 192.168.2.10/24, gateway 192.168.2.1
Refer to the exhibit. PC1 (192.168.1.10) cannot communicate with PC2 (192.168.2.10). What is the most likely cause?
⚠ Common exam trap
Many candidates assume a router automatically knows all networks in a topology, but routers only know directly connected networks unless routes are explicitly configured or learned via a routing protocol.
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
✓
Router1 lacks a route to the 192.168.2.0/24 network
Router1 lacks a route to the 192.168.2.0/24 network, so when PC1 sends traffic to PC2, Router1 does not have a destination network entry in its routing table to forward the packets. Without a route, the router drops the packets and may send an ICMP Destination Unreachable message back to PC1. This is the most likely cause because PC1 can reach its default gateway (Router1), but Router1 cannot forward traffic to the remote subnet.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
PC2 has an incorrect default gateway
Why it's wrong here
PC1 and PC2 sit on different subnets, so PC2's default gateway is irrelevant to PC1 reaching it; the failure lies with PC1's gateway or the router. A wrong default gateway on PC2 would break PC2's outbound traffic, making it tempting, but it cannot stop inbound connections to PC2.
- ✓
Router1 lacks a route to the 192.168.2.0/24 network
Why this is correct
PC1 and PC2 sit on different subnets, so traffic must be routed. Without a route for 192.168.2.0/24 in its routing table, Router1 drops the packets, breaking connectivity. The missing route is the specific fault preventing communication.
- ✗
Switch1 is not routing between VLANs
Why it's wrong here
A Layer 2 switch forwards frames within a VLAN and does not perform inter-VLAN routing; routing between 192.168.1.0/24 and 192.168.2.0/24 needs a router or Layer 3 switch. Blaming Switch1 is tempting because VLAN misconfiguration breaks connectivity, but the switch is not the device expected to route.
- ✗
PC1 has an incorrect subnet mask
Why it's wrong here
A wrong mask on PC1 would misalign its own subnet, but 192.168.1.10 and 192.168.2.10 sit in different /24 networks regardless, so PC1 would still route via its gateway. Masks matter when hosts share a prefix but disagree on its length; here the third octet already differs.
Visual reference
About these practice questions
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Same concept, more angles
1 more way this is tested on FC0-U71
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A technician is troubleshooting a workstation that cannot connect to a server at 192.168.1.100. The workstation's IP configuration shows: IP: 192.168.2.50, Subnet: 255.255.255.0, Gateway: 192.168.2.1. Which of the following is the MOST likely cause of the connectivity issue?
hard- A.Incorrect default gateway
- B.Incorrect subnet mask
- C.Duplicate IP address on the network
- ✓ D.Workstation and server are on different subnets with no routing
Why D: The workstation's IP address (192.168.2.50) and the server's IP address (192.168.1.100) belong to different subnets (192.168.2.0/24 and 192.168.1.0/24, respectively). Without a router configured to forward traffic between these subnets, the workstation cannot reach the server, even though the default gateway (192.168.2.1) is correct for its own subnet.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This FC0-U71 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the FC0-U71 exam.