The answer is to change the default-router in the DHCP pool 'LAN' to 192.168.1.1. This is correct because the PC received a valid IP address from the DHCP server, proving the pool’s network statement is accurate, but the default-router option is misconfigured to 192.168.1.254, which does not match the actual gateway interface IP of 192.168.1.1 on G0/0. The PC therefore uses an incorrect default gateway, preventing it from routing traffic to the internet. On the CCNA 200-301 v2 exam, this scenario tests your understanding of DHCP pool configuration and the critical role of the default-router command in providing the correct next-hop address for clients. A common trap is assuming the DHCP server is unreachable when the client gets an IP, but the real fault lies in the gateway mismatch. Remember the memory tip: “The default-router must mirror the router’s interface IP—if they don’t match, the client can’t catch the internet.”
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 connectivity issue for a remote worker who reports being unable to access the internet. The worker's PC is connected to switch S1, which is connected to router R1. You have console access to R1. The router's interface G0/0 is configured with IP 192.168.1.1/24, and the DHCP pool 'LAN' currently has network 192.168.1.0 255.255.255.0 and default-router 192.168.1.254. The PC has obtained an IP address of 192.168.1.100 from DHCP and a subnet mask of 255.255.255.0, but cannot ping 8.8.8.8. Identify the fault and configure R1 to restore internet access for the PC.
PC> ipconfig
Windows IP Configuration
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . :
IPv4 Address. . . . . . . . . . . : 169.254.10.55
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . : 0.0.0.0
R1# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 192.168.1.1 YES manual up up
GigabitEthernet0/1 10.0.0.1 YES manual up up
GigabitEthernet0/2 unassigned YES unset down down
R1# show running-config | section dhcp
ip dhcp excluded-address 192.168.1.1 192.168.1.10
!
ip dhcp pool LAN
network 192.168.1.0 255.255.255.0
default-router 192.168.1.254
dns-server 8.8.8.8
R1# show running-config interface GigabitEthernet0/0
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
no shutdown
!
A
Change the default-router in the DHCP pool 'LAN' to 192.168.1.1
The PC has an APIPA address because the DHCP server offers a default-router of 192.168.1.254, but the router's interface G0/0 is 192.168.1.1. The PC cannot reach the gateway, so it fails to get a valid IP. Changing the default-router to 192.168.1.1 matches the interface IP, allowing the PC to obtain a correct gateway and access the internet.
B
Change the network statement in the DHCP pool 'LAN' to 192.168.1.0 255.255.255.0
Why wrong: This is incorrect because the network statement defines the subnet from which DHCP assigns addresses. The PC's APIPA address indicates it is not receiving any DHCP offer, likely due to the gateway mismatch, not the network statement. The network statement is already correct for the 192.168.1.0/24 subnet.
C
Add the command 'ip helper-address 192.168.1.254' on interface G0/0
Why wrong: This is incorrect because ip helper-address is used to forward DHCP broadcasts to a remote DHCP server. Here, the DHCP server is local on R1, so no helper address is needed. Adding it would not resolve the gateway mismatch.
D
Change the IP address of interface G0/0 to 192.168.1.254/24
Why wrong: This is incorrect because changing the interface IP to 192.168.1.254 would match the current default-router, but it would break other configurations that rely on 192.168.1.1 (e.g., static routes, management access). The proper fix is to align the DHCP default-router with the existing interface IP.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Change the default-router in the DHCP pool 'LAN' to 192.168.1.1
The PC received a valid IP address from DHCP, proving the DHCP server is reachable and the network statement is correct. However, the pool’s default-router is set to 192.168.1.254, while the actual interface IP (the real gateway) is 192.168.1.1. The PC therefore uses an incorrect default gateway, blocking internet access. Changing the default-router to 192.168.1.1 fixes the gateway mismatch. Option B is wrong because the network statement already matches the subnet. Option C is unnecessary since no helper address is needed for a DHCP server on the same subnet. Option D would change the router’s IP to 192.168.1.254, creating further misalignment and breaking connectivity.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Change the default-router in the DHCP pool 'LAN' to 192.168.1.1
Why this is correct
The PC has an APIPA address because the DHCP server offers a default-router of 192.168.1.254, but the router's interface G0/0 is 192.168.1.1. The PC cannot reach the gateway, so it fails to get a valid IP. Changing the default-router to 192.168.1.1 matches the interface IP, allowing the PC to obtain a correct gateway and access the internet.
Change the network statement in the DHCP pool 'LAN' to 192.168.1.0 255.255.255.0
Why it's wrong here
This is incorrect because the network statement defines the subnet from which DHCP assigns addresses. The PC's APIPA address indicates it is not receiving any DHCP offer, likely due to the gateway mismatch, not the network statement. The network statement is already correct for the 192.168.1.0/24 subnet.
✗
Add the command 'ip helper-address 192.168.1.254' on interface G0/0
Why it's wrong here
This is incorrect because ip helper-address is used to forward DHCP broadcasts to a remote DHCP server. Here, the DHCP server is local on R1, so no helper address is needed. Adding it would not resolve the gateway mismatch.
✗
Change the IP address of interface G0/0 to 192.168.1.254/24
Why it's wrong here
This is incorrect because changing the interface IP to 192.168.1.254 would match the current default-router, but it would break other configurations that rely on 192.168.1.1 (e.g., static routes, management access). The proper fix is to align the DHCP default-router with the existing interface IP.
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.
✓Change the default-router in the DHCP pool 'LAN' to 192.168.1.1Correct answer▾
Why this is correct
The PC has an APIPA address because the DHCP server offers a default-router of 192.168.1.254, but the router's interface G0/0 is 192.168.1.1. The PC cannot reach the gateway, so it fails to get a valid IP. Changing the default-router to 192.168.1.1 matches the interface IP, allowing the PC to obtain a correct gateway and access the internet.
✗Change the network statement in the DHCP pool 'LAN' to 192.168.1.0 255.255.255.0Wrong answer — click to see why▾
Why this is wrong here
The network statement already matches the subnet; altering it does not fix the incorrect default gateway.
Why candidates choose this
Candidates may think the DHCP pool's network statement is wrong because the PC is not getting an IP, but the real issue is the default-router mismatch.
✗Add the command 'ip helper-address 192.168.1.254' on interface G0/0Wrong answer — click to see why▾
Why this is wrong here
A helper address is unnecessary when the DHCP server is on the same subnet as the client.
Why candidates choose this
Candidates may confuse this with scenarios where DHCP requests need to be relayed across subnets, but that is not the case here.
✗Change the IP address of interface G0/0 to 192.168.1.254/24Wrong answer — click to see why▾
Why this is wrong here
Changing the interface IP would make the router's address different from the subnet's actual gateway, further breaking connectivity.
Why candidates choose this
Candidates might think to make the interface IP match the default-router, but this is less efficient and could disrupt connectivity.
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: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Real-world example
How this comes up in practice
A network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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 block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Change the default-router in the DHCP pool 'LAN' to 192.168.1.1 — The PC received a valid IP address from DHCP, proving the DHCP server is reachable and the network statement is correct. However, the pool’s default-router is set to 192.168.1.254, while the actual interface IP (the real gateway) is 192.168.1.1. The PC therefore uses an incorrect default gateway, blocking internet access. Changing the default-router to 192.168.1.1 fixes the gateway mismatch. Option B is wrong because the network statement already matches the subnet. Option C is unnecessary since no helper address is needed for a DHCP server on the same subnet. Option D would change the router’s IP to 192.168.1.254, creating further misalignment and breaking connectivity.
What should I do if I get this 200-301 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related 200-301 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
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