CCNA DHCP default-router Practice Question
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.
⚠ Common exam trap
Do not assume that any connectivity issue is caused by a DHCP server failure; always compare the default-router entry in the DHCP pool with the actual interface IP before altering network statements or adding helper addresses. In this scenario, the PC obtained a valid IP, so the issue is not DHCP availability but a gateway mismatch.
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
✓
Change the default-router in the DHCP pool 'LAN' to 192.168.1.1
The PC received a valid IP address (192.168.1.100) 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.
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
Change the default-router to 192.168.1.1 to match the actual gateway IP on interface G0/0. The PC obtained a valid IP from DHCP, so the issue is not APIPA; it's a default gateway mismatch.
- ✗
Change the network statement in the DHCP pool 'LAN' to 192.168.1.0 255.255.255.0
Why it's wrong here
The network statement already matches the subnet; no change needed.
- ✗
Add the command 'ip helper-address 192.168.1.254' on interface G0/0
Why it's wrong here
No helper address is required because the DHCP server is on the same subnet as the PC.
- ✗
Change the IP address of interface G0/0 to 192.168.1.254/24
Why it's wrong here
Changing the interface IP would cause further misalignment and break connectivity.
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
Change the default-router to 192.168.1.1 to match the actual gateway IP on interface G0/0. The PC obtained a valid IP from DHCP, so the issue is not APIPA; it's a default gateway mismatch.
✗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?”
Visual reference
Quick reference
IPv4 Address Class Summary
| Class | First Octet Range | Default Mask | Networks | Hosts per Network |
|---|---|---|---|---|
| A | 1–126 | /8 (255.0.0.0) | 126 | 16,777,214 |
| B | 128–191 | /16 (255.255.0.0) | 16,384 | 65,534 |
| C | 192–223 | /24 (255.255.255.0) | 2,097,152 | 254 |
| D | 224–239 | N/A | Multicast groups | — |
| E | 240–255 | N/A | Reserved / experimental | — |
127.x.x.x is reserved for loopback. Modern networks use CIDR (classless) rather than classful addressing.
Go deeper
Related to this question
Learn chapter
DHCP Snooping
Key term
Switch
A switch is a networking device that connects devices on a local area network and uses MAC addresses to forward data only to the intended recipient.
Key term
LAN
Local Area Network — a network confined to a single physical location such as an office, building, or campus.
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JA
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.