- A
The port Gi0/24 has not been configured as a trusted port for DHCP snooping.
DHCP snooping immediately blocks all DHCP server messages on untrusted ports. Because Gi0/24 is the uplink to the DHCP server, it must be explicitly set as trusted (ip dhcp snooping trust), otherwise the switch will drop the DHCP offers sent by the server.
- B
The DHCP server is on a different subnet, and the VLAN 10 SVI does not have an ip helper-address configured.
Why wrong: If the server were on a different subnet, clients would have needed an IP helper address to obtain addresses even before DHCP snooping was enabled. Since they were receiving addresses prior to the change, an IP helper is either already configured or the server resides in the same broadcast domain. Enabling snooping does not alter this requirement.
- C
The DHCP snooping database location was not configured, causing the switch to discard all DHCP server messages.
Why wrong: The DHCP snooping database stores bindings for restoration after a reboot; it does not act as a real-time filter. Without a database, the switch still forwards DHCP messages normally and populates the binding table in memory. Server messages are not dropped because of an absent database.
- D
The DHCP snooping binding table does not contain an entry for the DHCP server’s MAC address, so offers are being discarded.
Why wrong: The binding table maps client IP addresses, MAC addresses, lease times, and ports; it does not store entries for DHCP servers. The switch does not need to learn the server’s MAC to forward DHCP traffic. The table is used to validate client messages like DHCPRELEASE or DECLINE, not to permit server messages.
Quick Answer
The answer is that the port Gi0/24 has not been configured as a trusted port for DHCP snooping. This is the most likely cause because DHCP snooping treats all ports as untrusted by default, and an untrusted port will drop all DHCP server messages like OFFER and ACK to block rogue servers. Since the legitimate DHCP server is connected to Gi0/24, its offers are being discarded, so clients never receive IP addresses. On the CCNA 200-301 v2 exam, this question tests your understanding of the DHCP snooping trust boundary—a core security feature that prevents unauthorized DHCP servers from handing out addresses. A common trap is assuming the server’s traffic is automatically allowed, but the default untrusted state explicitly blocks it. Remember the memory tip: “Trust the uplink, block the rest”—always configure the port facing the legitimate DHCP server with the ip dhcp snooping trust command.
CCNA Network Services and Security Practice Question
This 200-301 practice question tests your understanding of network services and security. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
After enabling DHCP snooping on VLAN 10, a technician finds that clients in that VLAN are no longer receiving IP addresses from the DHCP server. The server is connected to port Gi0/24. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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 port Gi0/24 has not been configured as a trusted port for DHCP snooping.
DHCP snooping classifies all ports as untrusted by default, and an untrusted port drops DHCP server messages (OFFER/ACK) to prevent rogue servers. Because the uplink Gi0/24 was not explicitly configured as a trusted port with ip dhcp snooping trust, the legitimate DHCP offers from the server are being discarded, so clients never receive addresses. The other options are not the cause: an ip helper-address would still be needed if the server were remote and was working before snooping (so it is already in place); the DHCP snooping database is not required for traffic forwarding; and the binding table does not need to contain the server’s MAC to permit server traffic.
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.
- ✓
The port Gi0/24 has not been configured as a trusted port for DHCP snooping.
Why this is correct
DHCP snooping immediately blocks all DHCP server messages on untrusted ports. Because Gi0/24 is the uplink to the DHCP server, it must be explicitly set as trusted (ip dhcp snooping trust), otherwise the switch will drop the DHCP offers sent by the server.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
- ✗
The DHCP server is on a different subnet, and the VLAN 10 SVI does not have an ip helper-address configured.
Why it's wrong here
If the server were on a different subnet, clients would have needed an IP helper address to obtain addresses even before DHCP snooping was enabled. Since they were receiving addresses prior to the change, an IP helper is either already configured or the server resides in the same broadcast domain. Enabling snooping does not alter this requirement.
- ✗
The DHCP snooping database location was not configured, causing the switch to discard all DHCP server messages.
Why it's wrong here
The DHCP snooping database stores bindings for restoration after a reboot; it does not act as a real-time filter. Without a database, the switch still forwards DHCP messages normally and populates the binding table in memory. Server messages are not dropped because of an absent database.
- ✗
The DHCP snooping binding table does not contain an entry for the DHCP server’s MAC address, so offers are being discarded.
Why it's wrong here
The binding table maps client IP addresses, MAC addresses, lease times, and ports; it does not store entries for DHCP servers. The switch does not need to learn the server’s MAC to forward DHCP traffic. The table is used to validate client messages like DHCPRELEASE or DECLINE, not to permit server messages.
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 port Gi0/24 has not been configured as a trusted port for DHCP snooping.Correct answer▾
Why this is correct
DHCP snooping immediately blocks all DHCP server messages on untrusted ports. Because Gi0/24 is the uplink to the DHCP server, it must be explicitly set as trusted (ip dhcp snooping trust), otherwise the switch will drop the DHCP offers sent by the server.
✗The DHCP server is on a different subnet, and the VLAN 10 SVI does not have an ip helper-address configured.Wrong answer — click to see why▾
Why this is wrong here
This option assumes that the loss of DHCP service is due to a missing relay agent, but the symptom started only after enabling snooping, not after an infrastructure change that would affect the relay path.
✗The DHCP snooping database location was not configured, causing the switch to discard all DHCP server messages.Wrong answer — click to see why▾
Why this is wrong here
The idea that a missing database causes immediate traffic blocking is a common misinterpretation of the database’s role—it is purely for persistency, not for runtime filtering.
✗The DHCP snooping binding table does not contain an entry for the DHCP server’s MAC address, so offers are being discarded.Wrong answer — click to see why▾
Why this is wrong here
Many candidates assume that DHCP snooping uses a reverse-check against the binding table for any DHCP server messages, but the filtering is based solely on the trusted/untrusted port state, not on a learned server entry.
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.
What to study next
Got this wrong? Here's your next step.
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.
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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 — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The port Gi0/24 has not been configured as a trusted port for DHCP snooping. — DHCP snooping classifies all ports as untrusted by default, and an untrusted port drops DHCP server messages (OFFER/ACK) to prevent rogue servers. Because the uplink Gi0/24 was not explicitly configured as a trusted port with ip dhcp snooping trust, the legitimate DHCP offers from the server are being discarded, so clients never receive addresses. The other options are not the cause: an ip helper-address would still be needed if the server were remote and was working before snooping (so it is already in place); the DHCP snooping database is not required for traffic forwarding; and the binding table does not need to contain the server’s MAC to permit server traffic.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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Last reviewed: Jun 14, 2026
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