- A
The ip helper-address command has been incorrectly applied to VLAN 100 instead of VLAN 200.
Why wrong: The helper must be on the client VLAN's SVI to convert broadcast requests to unicast. Placing it on VLAN 200 would not forward the clients' broadcasts.
- B
The switch port that connects to the DHCP server's VLAN is not configured as a trusted DHCP snooping port.
DHCP snooping classifies ports as trusted or untrusted. Server-originated DHCP messages (Offer/ACK) are only allowed on trusted ports. The server's response comes from VLAN 200, so the interface facing that server must be trusted.
- C
DHCP snooping must be disabled globally because it conflicts with the configured DHCP relay agent.
Why wrong: Relay agents forward requests to the server without interfering with snooping. The two features can coexist if the server-facing port is trusted.
- D
The DHCP server lacks a valid default gateway, preventing replies from reaching the relay agent's SVI subnet.
Why wrong: The switch confirms the server is reachable, implying correct routing. The relay agent uses its SVI IP as the source, and the server replies directly; no additional gateway configuration is needed.
Quick Answer
The answer is that the switch port connecting to the legitimate DHCP server’s VLAN is not configured as a trusted DHCP snooping port. This is correct because DHCP snooping treats all ports as untrusted by default, meaning the switch will drop any DHCP server messages—such as OFFER and ACK packets—that arrive on an untrusted interface. Even though the switch’s SVI can reach the server and relay the request, the server’s reply enters the switch on an untrusted port, so DHCP snooping blocks it before the switch can forward the lease to the client. On the CCNA 200-301 v2 exam, this scenario tests your understanding of how DHCP snooping’s trust boundary works, often appearing as a troubleshooting question where the engineer forgets to mark the uplink port as trusted. A common trap is assuming that because the switch can ping the server, the relayed reply will pass through; in reality, DHCP snooping filters at Layer 2, not Layer 3. Remember the memory tip: “Trust the server port, or the OFFER gets caught short.”
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 engineer has implemented DHCP snooping on a Cisco switch to prevent unauthorized DHCP servers. The switch's VLAN 100 SVI is configured with ip helper-address to relay DHCP requests to a legitimate server in VLAN 200. Clients in VLAN 100 cannot obtain IP leases, even though the DHCP server is reachable from the switch and has available addresses.
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
The switch port that connects to the DHCP server's VLAN is not configured as a trusted DHCP snooping port.
DHCP snooping treats all switch ports as untrusted by default, which blocks DHCP server messages (OFFER, ACK) from entering the switch. Even though the switch itself can reach the DHCP server, the relayed reply from the server arrives on a port that is not trusted, so DHCP snooping drops the packet before it can be forwarded to the client. Configuring the port connecting to the DHCP server as a trusted port allows the server's responses to pass through the switch, resolving the issue.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The ip helper-address command has been incorrectly applied to VLAN 100 instead of VLAN 200.
- ✓
The switch port that connects to the DHCP server's VLAN is not configured as a trusted DHCP snooping port.
Why this is correct
DHCP snooping classifies ports as trusted or untrusted. Server-originated DHCP messages (Offer/ACK) are only allowed on trusted ports. The server's response comes from VLAN 200, so the interface facing that server must be trusted.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
DHCP snooping must be disabled globally because it conflicts with the configured DHCP relay agent.
Why it's wrong here
Relay agents forward requests to the server without interfering with snooping. The two features can coexist if the server-facing port is trusted.
- ✗
The DHCP server lacks a valid default gateway, preventing replies from reaching the relay agent's SVI subnet.
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.
✓The switch port that connects to the DHCP server's VLAN is not configured as a trusted DHCP snooping port.Correct answer▾
Why this is correct
DHCP snooping classifies ports as trusted or untrusted. Server-originated DHCP messages (Offer/ACK) are only allowed on trusted ports. The server's response comes from VLAN 200, so the interface facing that server must be trusted.
✗The ip helper-address command has been incorrectly applied to VLAN 100 instead of VLAN 200.Wrong answer — click to see why▾
Why this is wrong here
Many engineers mistakenly think the helper should reside on the server VLAN; however, it must reside on the client-facing L3 interface.
✗DHCP snooping must be disabled globally because it conflicts with the configured DHCP relay agent.Wrong answer — click to see why▾
Why this is wrong here
A common misconception is that DHCP relay bypasses snooping, but snooping still inspects the server's unicast response and drops it unless the ingress port is trusted.
✗The DHCP server lacks a valid default gateway, preventing replies from reaching the relay agent's SVI subnet.Wrong answer — click to see why▾
Why this is wrong here
Candidates often suspect routing issues, but verified reachability eliminates this. The problem lies in the snooping policy, not IP 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: answer the scenario, not the keyword
Cisco often tests the interaction between DHCP snooping and DHCP relay, where candidates mistakenly think the relay bypasses snooping or that the issue is with the helper-address configuration, rather than the untrusted port blocking the server's unicast reply.
Detailed technical explanation
How to think about this question
DHCP snooping builds a DHCP snooping binding table by monitoring DHCP messages on trusted ports; untrusted ports only allow DHCP DISCOVER and REQUEST messages from clients, while blocking all server messages (OFFER, ACK, NAK). When ip helper-address is configured, the switch acts as a DHCP relay agent, changing the source IP to its own SVI address and unicasting the request to the server; the server's unicast reply arrives on the switch port, but DHCP snooping inspects the packet and drops it if the port is untrusted, even though the packet is not a broadcast. In a real-world scenario, this often occurs when a network engineer adds DHCP snooping to an existing relay setup without remembering to configure the uplink port to the DHCP server as trusted.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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.
What to study next
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The switch port that connects to the DHCP server's VLAN is not configured as a trusted DHCP snooping port. — DHCP snooping treats all switch ports as untrusted by default, which blocks DHCP server messages (OFFER, ACK) from entering the switch. Even though the switch itself can reach the DHCP server, the relayed reply from the server arrives on a port that is not trusted, so DHCP snooping drops the packet before it can be forwarded to the client. Configuring the port connecting to the DHCP server as a trusted port allows the server's responses to pass through the switch, resolving the issue.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 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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