CCNA Network Infrastructure and Connectivity Practice Question
This 200-301 practice question tests your understanding of network infrastructure and connectivity. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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>
PC1> ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . : example.local
Link-local IPv6 Address . . . . . : fe80::1a2b:3c4d:5e6f:7a8b%11
IPv4 Address. . . . . . . . . . . : 169.254.123.45
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
PC1> ping 8.8.8.8
Pinging 8.8.8.8 with 32 bytes of data:
Reply from 169.254.123.45: Destination host unreachable.
Reply from 169.254.123.45: Destination host unreachable.
R1# show ip dhcp binding
Bindings from all pools not associated with VRF:
IP address Client-ID/ Lease expiration Type
Hardware address/
User name
192.168.1.10 0100.1111.2222.3333 Mar 01 2025 12:00 PM Automatic
R1# show ip dhcp pool
Pool LANPOOL:
Utilization mark (high/low) : 100 / 0
Subnet size (first/next) : 0 / 0
Total addresses : 254
Leased addresses : 1
Pending event : none
1 network(s) exist
Network number : 192.168.1.0
Mask : 255.255.255.0
Default router : 192.168.1.1
DNS server : 8.8.8.8
Lease time (min) : 1440
SW1# show vlan brief
VLAN Name Status Ports
---- -------------------------------- --------- -------------------------------
1 default active G0/1, G0/2
SW1# show interfaces g0/2 switchport
Name: G0/2
Switchport: Enabled
Administrative Mode: static access
Operational Mode: static access
Administrative Trunking Encapsulation: dot1q
Operational Trunking Encapsulation: native
Negotiation of Trunking: Off
Access Mode VLAN: 1 (default)
Trunking Native Mode VLAN: 1 (default)
Administrative Native VLAN tagging: enabled
Voice VLAN: none
A
Configure R1's interface G0/0 with IP address 192.168.1.1/24 and ensure the interface is not administratively down.
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.
B
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 wrong: 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.
C
Enable DHCP snooping on SW1 and configure the port G0/2 as a trusted port.
Why wrong: 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.
D
Configure a static IP address of 192.168.1.10/24 on the PC with default gateway 192.168.1.1.
Why wrong: 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.
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.
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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.
Related concept
Access ports place end devices into a single VLAN.
✗
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?”
Common exam traps
Common exam trap: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Trap categories for this question
Command / output trap
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.
Scenario analysis trap
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.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
→Use show vlan brief to verify access VLANs.
→Use show interfaces trunk to verify trunk state and allowed VLANs.
→Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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