The answer is to enable the physical interface GigabitEthernet0/0 with the 'no shutdown' command. This is correct because a subinterface like G0/0.10 is a logical division of the parent interface; if the physical GigabitEthernet0/0 is administratively down, the subinterface cannot pass traffic regardless of its own IP configuration. When you troubleshoot subinterface down parent interface shutdown scenarios on the CCNA 200-301 v2 exam, the key concept is that subinterfaces inherit the operational state of their parent—a shutdown physical interface blocks all associated VLANs and subnets. A common trap is to check the subinterface configuration first, but the real issue is often the parent interface being disabled. Remember the memory tip: "Parent first, child second"—always verify the physical interface status before troubleshooting subinterface connectivity, as no amount of subinterface configuration will work if the parent is shut down.
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 wired client connectivity issue on VLAN 10. PC1 (192.168.10.50/24) cannot reach the internet. The gateway is R1's subinterface G0/0.10 at 192.168.10.1. R1 has a default route to ISP router 203.0.113.1. From PC1, ping 192.168.10.1 fails, but ipconfig shows correct IP. Analyze the provided outputs and fix the problem on R1 so that PC1 can ping its default gateway.
R1# show running-config | section interface GigabitEthernet0/0
interface GigabitEthernet0/0
no ip address
duplex auto
speed auto
!
interface GigabitEthernet0/0.10
encapsulation dot1Q 10
ip address 192.168.10.1 255.255.255.0
!
R1# show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
C 192.168.10.0/24 is directly connected, GigabitEthernet0/0.10
PC1> ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 192.168.10.50
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.10.1
PC1> ping 192.168.10.1
Pinging 192.168.10.1 with 32 bytes of data:
Reply from 192.168.10.50: Destination host unreachable.
Reply from 192.168.10.50: Destination host unreachable.
Reply from 192.168.10.50: Destination host unreachable.
Reply from 192.168.10.50: Destination host unreachable.
Ping statistics for 192.168.10.1:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),
A
Enable the physical interface GigabitEthernet0/0 with 'no shutdown'.
The physical interface GigabitEthernet0/0 is administratively down, so the subinterface G0/0.10 cannot forward frames. 'No shutdown' brings the interface up, allowing PC1 to ping its gateway 192.168.10.1 and reach the internet via the existing default route.
B
Configure 'no shutdown' on subinterface G0/0.10 and add a static route for 192.168.10.0/24 pointing to the ISP.
Why wrong: Subinterfaces do not have a separate 'shutdown' state; they inherit the state of the physical interface. Also, a static route for the local VLAN is unnecessary because the directly connected network is already in the routing table. The issue is the physical interface being down and the missing default route.
C
Change the IP address of subinterface G0/0.10 to 192.168.10.254 and add a default route via 203.0.113.1.
Why wrong: The IP address 192.168.10.1 is correct as the gateway; changing it would cause a mismatch with PC1's configured gateway. The physical interface still needs to be enabled. The default route is needed, but the IP change is incorrect.
D
Enable VLAN 10 on the switch and configure trunking between the switch and R1.
Why wrong: The problem is on R1, not the switch. The PC can ping other devices on VLAN 10? The issue is that R1's physical interface is down, preventing any traffic from reaching the router. Switch configuration is irrelevant if the router interface is administratively down.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Enable the physical interface GigabitEthernet0/0 with 'no shutdown'.
PC1 has a correct IP configuration and can reach its gateway IP 192.168.10.1 now that the physical interface is no longer administratively down. The R1 subinterface G0/0.10 already has the correct IP address, but the parent interface GigabitEthernet0/0 was shut down, preventing the subinterface from passing traffic. Issuing 'no shutdown' under the main interface restores connectivity because subinterfaces depend on the physical interface being up. The default route to 203.0.113.1 was already present as stated in the stem, so no routing change is needed.
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.
✓
Enable the physical interface GigabitEthernet0/0 with 'no shutdown'.
Why this is correct
The physical interface GigabitEthernet0/0 is administratively down, so the subinterface G0/0.10 cannot forward frames. 'No shutdown' brings the interface up, allowing PC1 to ping its gateway 192.168.10.1 and reach the internet via the existing default route.
Related concept
Access ports place end devices into a single VLAN.
✗
Configure 'no shutdown' on subinterface G0/0.10 and add a static route for 192.168.10.0/24 pointing to the ISP.
Why it's wrong here
Subinterfaces do not have a separate 'shutdown' state; they inherit the state of the physical interface. Also, a static route for the local VLAN is unnecessary because the directly connected network is already in the routing table. The issue is the physical interface being down and the missing default route.
✗
Change the IP address of subinterface G0/0.10 to 192.168.10.254 and add a default route via 203.0.113.1.
Why it's wrong here
The IP address 192.168.10.1 is correct as the gateway; changing it would cause a mismatch with PC1's configured gateway. The physical interface still needs to be enabled. The default route is needed, but the IP change is incorrect.
✗
Enable VLAN 10 on the switch and configure trunking between the switch and R1.
Why it's wrong here
The problem is on R1, not the switch. The PC can ping other devices on VLAN 10? The issue is that R1's physical interface is down, preventing any traffic from reaching the router. Switch configuration is irrelevant if the router interface is administratively down.
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.
✓Enable the physical interface GigabitEthernet0/0 with 'no shutdown'.Correct answer▾
Why this is correct
The physical interface GigabitEthernet0/0 is administratively down, so the subinterface G0/0.10 cannot forward frames. 'No shutdown' brings the interface up, allowing PC1 to ping its gateway 192.168.10.1 and reach the internet via the existing default route.
✗Configure 'no shutdown' on subinterface G0/0.10 and add a static route for 192.168.10.0/24 pointing to the ISP.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: Subinterfaces cannot be individually shut/no shut; they depend on the physical interface. Also, adding a route for the local network is redundant.
Why candidates choose this
Candidates may think subinterfaces need to be enabled separately and that a route for the local network is required for internet access.
✗Change the IP address of subinterface G0/0.10 to 192.168.10.254 and add a default route via 203.0.113.1.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The gateway IP must match the PC's configured default gateway. Changing it would break connectivity even if the interface were up.
Why candidates choose this
Candidates might think the gateway IP is wrong because the ping fails, or they may confuse the gateway with the network address.
✗Enable VLAN 10 on the switch and configure trunking between the switch and R1.Wrong answer — click to see why▾
Why this is wrong here
The specific factual error: The switch configuration may be correct; the issue is specifically on R1's interface. The question asks to fix the problem on R1.
Why candidates choose this
Candidates may assume the problem is with VLAN or trunking because the PC is on VLAN 10, but the outputs indicate the router interface is down.
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.
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: Enable the physical interface GigabitEthernet0/0 with 'no shutdown'. — PC1 has a correct IP configuration and can reach its gateway IP 192.168.10.1 now that the physical interface is no longer administratively down. The R1 subinterface G0/0.10 already has the correct IP address, but the parent interface GigabitEthernet0/0 was shut down, preventing the subinterface from passing traffic. Issuing 'no shutdown' under the main interface restores connectivity because subinterfaces depend on the physical interface being up. The default route to 203.0.113.1 was already present as stated in the stem, so no routing change is needed.
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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