CCNA Network Infrastructure and Connectivity Practice Question
Network Topology
You are troubleshooting a PC connected to switch SW1. The PC cannot access the internet. SW1 is connected to router R1 via port G0/1. R1 provides default gateway and DHCP services. Analyze the provided show output and fix the connectivity issue so that the PC can ping 8.8.8.8.
=== Show output from R1 === <pre>
R1# show ip interface brief Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 unassigned YES manual administratively down down GigabitEthernet0/1 10.0.0.1 YES NVRAM up up </pre>
=== Show output from PC === <pre>
C:\> ipconfig
Ethernet adapter Ethernet0: Connection-specific DNS Suffix . : IPv4 Address. . . . . . . . . . : 169.254.123.45 Subnet Mask . . . . . . . . . . : 255.255.0.0 Default Gateway . . . . . . . . : </pre>
=== Show output from SW1 === <pre>
SW1# show vlan brief VLAN Name Status Ports
---- -------------------------------- --------- ------------------------------- 1 default active Gi0/1, Gi0/2, Gi0/3 </pre>
⚠ Common exam trap
This question tests your ability to identify that a router interface must have an IP address in the client subnet for DHCP to work, even if the DHCP pool is correctly configured. Many candidates focus on VLANs or DHCP server settings but overlook the basic requirement of an IP address on the router interface.
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
✓
Configure R1's interface G0/0 with IP address 192.168.1.1/24 and ensure the interface is not administratively down.
The PC's APIPA address (169.254.x.x) indicates DHCP failure. The router's DHCP pool is correctly configured and has a lease, but the show output reveals that R1's interface G0/0 is administratively down and has no IP address. Without a working IP on G0/0, the router cannot serve DHCP or route traffic for VLAN 1, even though both the PC and the router are in the same VLAN. Option A fixes the root cause by assigning the correct subnet IP and bringing the interface up. Option B is incorrect because moving the PC to a different VLAN or creating subinterfaces does nothing to enable the router's physical interface where DHCP and routing must run. Option C is wrong because DHCP snooping or trust configurations are irrelevant when the router's own interface is down/unaddressed. Option D is a workaround that only masks the problem; the scenario requires a working DHCP service, and a static IP would not restore the intended design.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Configure R1's interface G0/0 with IP address 192.168.1.1/24 and ensure the interface is not administratively down.
Why this is correct
The PC has an APIPA address (169.254.123.45) indicating DHCP failure. The DHCP pool on R1 is correctly configured for the 192.168.1.0/24 subnet, but R1's interface G0/0 (connected to SW1) lacks an IP address in that subnet. Without an IP address on the interface, R1 cannot act as the default gateway or respond to DHCP requests. Configuring 192.168.1.1/24 on G0/0 and ensuring it is up will allow DHCP to function and provide the PC with a valid IP address, enabling internet access.
- ✗
Change the VLAN on SW1's port G0/2 to VLAN 10 and configure R1's subinterface G0/0.10 with IP 192.168.1.1/24.
Why it's wrong here
This is incorrect because the PC and R1 are already in VLAN 1, and there is no need for a different VLAN or subinterface. The existing configuration shows both devices are in VLAN 1, so adding a new VLAN and subinterface would complicate the network unnecessarily and not fix the missing IP address on R1's interface.
- ✗
Enable DHCP snooping on SW1 and configure the port G0/2 as a trusted port.
Why it's wrong here
This is incorrect because DHCP snooping is a security feature to prevent rogue DHCP servers. In this scenario, the DHCP server is legitimate and on R1. The issue is not security-related; it is a basic connectivity problem due to the missing IP address on R1's interface.
- ✗
Configure a static IP address of 192.168.1.10/24 on the PC with default gateway 192.168.1.1.
Why it's wrong here
This is incorrect because while a static IP could temporarily fix connectivity, the question asks to fix the issue so the PC can ping 8.8.8.8. The underlying problem is that R1's interface lacks an IP address, so even with a static IP, the PC would not have a default gateway that is reachable. The correct solution is to configure the router interface.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
✓Configure R1's interface G0/0 with IP address 192.168.1.1/24 and ensure the interface is not administratively down.Correct answer▾
Why this is correct
The PC has an APIPA address (169.254.123.45) indicating DHCP failure. The DHCP pool on R1 is correctly configured for the 192.168.1.0/24 subnet, but R1's interface G0/0 (connected to SW1) lacks an IP address in that subnet. Without an IP address on the interface, R1 cannot act as the default gateway or respond to DHCP requests. Configuring 192.168.1.1/24 on G0/0 and ensuring it is up will allow DHCP to function and provide the PC with a valid IP address, enabling internet access.
✗Change the VLAN on SW1's port G0/2 to VLAN 10 and configure R1's subinterface G0/0.10 with IP 192.168.1.1/24.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that the problem is not a VLAN mismatch; it is the absence of an IP address on R1's interface. Changing VLANs would not resolve the DHCP failure.
Why candidates choose this
Candidates might think that DHCP requires a different subnet or VLAN, or they may confuse this scenario with router-on-a-stick configurations where subinterfaces are used for inter-VLAN routing.
✗Enable DHCP snooping on SW1 and configure the port G0/2 as a trusted port.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that DHCP snooping does not fix the absence of an IP address on the router interface. It only filters DHCP messages based on trust settings.
Why candidates choose this
Candidates may think that DHCP snooping is required to allow DHCP traffic across switches, or they may confuse this with scenarios where DHCP is failing due to rogue servers or untrusted ports.
✗Configure a static IP address of 192.168.1.10/24 on the PC with default gateway 192.168.1.1.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error is that configuring a static IP on the PC does not address the missing IP address on R1's interface. The router must have an IP in the same subnet to route traffic.
Why candidates choose this
Candidates might think that since DHCP failed, a static IP is a quick fix. However, they overlook that the router interface is not configured, so the default gateway would be unreachable.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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Related to this question
Learn chapter
IPv4 Addressing and Address Classes
Key term
Interface
An interface is a point of connection or interaction between two systems, devices, or software components that allows them to exchange information or signals.
Key term
Route
A route is a path that data takes through a network from one device or network to another, determined by routing protocols and configured rules.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 200-301 practice question is part of Courseiva's free Cisco 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 200-301 exam.