- A
Check the DHCP server logs for any error or warning messages related to the clients' requests.
Why wrong: The server logs will not show any incoming DHCP discovers from these clients because the router is not forwarding them from the correct interface. Investigating server logs would be a waste of time when the configuration error is already visible.
- B
Move the ip helper-address command from interface Gi0/0 to interface Gi0/1.
DHCP relay requires the helper address to be configured on the interface that faces the DHCP clients (the broadcast domain where clients send their DHCPDISCOVER messages). By moving the command to Gi0/1, the router will correctly intercept and forward client requests to the DHCP server.
- C
Issue the show ip interface brief command to ensure that interface Gi0/1 is in an up/up state.
Why wrong: Checking interface status is a basic step, but the technician would have noticed if the interface were down from the start. Moreover, the router's running config was already examined, so the interface must be at least administratively up for the technician to have been troubleshooting client connectivity. The core issue is the helper-address placement, not the interface state.
- D
Remove the ip helper-address from Gi0/0 and then reapply it to the same interface to ensure the command is active.
Why wrong: Reapplying the command to the wrong interface does not change the behavior; the router will still not see client DHCP broadcasts on the WAN link. The helper address must be on the interface that receives the broadcasts.
Quick Answer
The correct answer is to move the ip helper-address command from interface Gi0/0 to interface Gi0/1. This is because the DHCP relay helper address must be placed on the client-facing interface—the one that receives the client’s DHCP broadcast—so the router can intercept that broadcast and forward it as a unicast to the central DHCP server. Placing it on the WAN interface (Gi0/0) means the router never sees the client’s DHCP Discover message, so no relay occurs. On the CCNA 200-301 v2 exam, this scenario tests your understanding of DHCP relay operation at the network services layer, and a common trap is assuming the helper address goes on the interface closest to the server. A reliable memory tip is “helper goes toward the host, not the hub”—the ip helper-address command belongs on the LAN-facing interface where clients broadcast, not on the uplink toward the DHCP server.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. 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.
A network technician is troubleshooting a DHCP relay issue. The router at the branch office is supposed to forward DHCP requests from local clients to a central DHCP server. Clients connected to Gi0/1 are not receiving IP addresses. The technician verifies that the DHCP server is reachable from the router, that no ACLs are blocking DHCP traffic, and that the DHCP scope on the server has available leases. Upon checking the running configuration, the technician notices that the ip helper-address command is applied to interface Gi0/0 (the WAN link toward the server) instead of Gi0/1. What should the technician do next?
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
Move the ip helper-address command from interface Gi0/0 to interface Gi0/1.
The ip helper-address command must be configured on the interface that receives DHCP broadcasts from clients—in this case, Gi0/1, the LAN-facing interface. Placing it on the WAN interface (Gi0/0) means the router never sees the client broadcasts and therefore never relays them. Moving the command to Gi0/1 enables the router to intercept DHCP discoveries and forward them as unicast packets to the DHCP server. This action directly addresses a common DHCP relay misconfiguration at the network services layer.
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.
- ✗
Check the DHCP server logs for any error or warning messages related to the clients' requests.
Why it's wrong here
The server logs will not show any incoming DHCP discovers from these clients because the router is not forwarding them from the correct interface. Investigating server logs would be a waste of time when the configuration error is already visible.
- ✓
Move the ip helper-address command from interface Gi0/0 to interface Gi0/1.
Why this is correct
DHCP relay requires the helper address to be configured on the interface that faces the DHCP clients (the broadcast domain where clients send their DHCPDISCOVER messages). By moving the command to Gi0/1, the router will correctly intercept and forward client requests to the DHCP server.
Related concept
CIDR notation defines the prefix length.
- ✗
Issue the show ip interface brief command to ensure that interface Gi0/1 is in an up/up state.
Why it's wrong here
Checking interface status is a basic step, but the technician would have noticed if the interface were down from the start. Moreover, the router's running config was already examined, so the interface must be at least administratively up for the technician to have been troubleshooting client connectivity. The core issue is the helper-address placement, not the interface state.
- ✗
Remove the ip helper-address from Gi0/0 and then reapply it to the same interface to ensure the command is active.
Why it's wrong here
Reapplying the command to the wrong interface does not change the behavior; the router will still not see client DHCP broadcasts on the WAN link. The helper address must be on the interface that receives the broadcasts.
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.
✓Move the ip helper-address command from interface Gi0/0 to interface Gi0/1.Correct answer▾
Why this is correct
DHCP relay requires the helper address to be configured on the interface that faces the DHCP clients (the broadcast domain where clients send their DHCPDISCOVER messages). By moving the command to Gi0/1, the router will correctly intercept and forward client requests to the DHCP server.
✗Check the DHCP server logs for any error or warning messages related to the clients' requests.Wrong answer — click to see why▾
Why this is wrong here
This skips the obvious configuration mismatch and targets the wrong component. It assumes the issue is on the server side rather than the router's DHCP relay placement.
✗Issue the show ip interface brief command to ensure that interface Gi0/1 is in an up/up state.Wrong answer — click to see why▾
Why this is wrong here
This action investigates Layer 1/2 status when the problem is already identified as a Layer 3 (DHCP relay) configuration error. It skips applying the fix and delays resolution.
✗Remove the ip helper-address from Gi0/0 and then reapply it to the same interface to ensure the command is active.Wrong answer — click to see why▾
Why this is wrong here
Candidates might think the command simply didn't take effect and that reapplying it solves the problem, misunderstanding the directional requirement of DHCP relay placement.
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.
Trap categories for this question
Command / output trap
The server logs will not show any incoming DHCP discovers from these clients because the router is not forwarding them from the correct interface. Investigating server logs would be a waste of time when the configuration error is already visible.
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 security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
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.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Network Services and Security — This question tests Network Services and Security — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Move the ip helper-address command from interface Gi0/0 to interface Gi0/1. — The ip helper-address command must be configured on the interface that receives DHCP broadcasts from clients—in this case, Gi0/1, the LAN-facing interface. Placing it on the WAN interface (Gi0/0) means the router never sees the client broadcasts and therefore never relays them. Moving the command to Gi0/1 enables the router to intercept DHCP discoveries and forward them as unicast packets to the DHCP server. This action directly addresses a common DHCP relay misconfiguration at the network services layer.
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.
About these practice questions
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Last reviewed: Jun 14, 2026
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.
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