- A
DHCP snooping is configured on Layer 2 switches to filter DHCP messages on untrusted ports.
Correct because DHCP snooping is a Layer 2 security feature implemented on switches.
- B
The DHCP snooping binding table includes the client MAC address, IP address, lease time, VLAN, and port number.
Correct because these are the fields stored in the DHCP snooping database.
- C
Ports connected to DHCP servers should be configured as trusted ports.
Correct because trusted ports are allowed to send DHCP server messages without filtering.
- D
The DHCP snooping binding database is stored in NVRAM by default.
Why wrong: Incorrect because the database is stored in flash memory, not NVRAM.
- E
DHCP snooping validates DHCPv6 messages by default when enabled globally.
Why wrong: Incorrect because DHCPv6 snooping requires separate configuration and is not enabled by default with DHCP snooping.
Quick Answer
The answer is that ports connected to DHCP servers should be configured as trusted ports. This is correct because DHCP snooping operates by dividing switch ports into trusted and untrusted categories; trusted ports are allowed to send DHCP server messages (like OFFER and ACK), while untrusted ports, typically facing clients, have these messages filtered out to prevent rogue DHCP server attacks. On the ENCOR 350-401 exam, this concept tests your understanding of Layer 2 security mechanisms, often appearing in multiple-choice questions where you must identify true statements about DHCP snooping features. A common trap is confusing the storage location of the binding database—it is kept in flash memory, not NVRAM—or assuming DHCP snooping applies to DHCPv6 by default, which it does not. Remember the memory tip: "Trust the server, distrust the client" to quickly recall that trusted ports face upstream DHCP servers.
CCNP Infrastructure Security Practice Question
This 350-401 practice question tests your understanding of infrastructure 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.
Which three statements about DHCP snooping are true? (Choose three.)
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
DHCP snooping is configured on Layer 2 switches to filter DHCP messages on untrusted ports.
DHCP snooping is a security feature that filters untrusted DHCP messages and builds a binding database. It is configured on switches, not routers. The DHCP snooping binding table contains the client MAC address, IP address, lease time, VLAN, and port. Trusted ports are typically uplinks to DHCP servers, while untrusted ports face clients. Option D is incorrect because the DHCP snooping database is stored in the switch's flash memory, not NVRAM. Option E is incorrect because DHCP snooping does not validate DHCPv6 messages by default; it is for DHCPv4 only unless DHCPv6 snooping is separately configured.
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.
- ✓
DHCP snooping is configured on Layer 2 switches to filter DHCP messages on untrusted ports.
Why this is correct
Correct because DHCP snooping is a Layer 2 security feature implemented on switches.
Related concept
Access ports place end devices into a single VLAN.
- ✓
The DHCP snooping binding table includes the client MAC address, IP address, lease time, VLAN, and port number.
Why this is correct
Correct because these are the fields stored in the DHCP snooping database.
Related concept
Access ports place end devices into a single VLAN.
- ✓
Ports connected to DHCP servers should be configured as trusted ports.
- ✗
The DHCP snooping binding database is stored in NVRAM by default.
Why it's wrong here
Incorrect because the database is stored in flash memory, not NVRAM.
- ✗
DHCP snooping validates DHCPv6 messages by default when enabled globally.
Why it's wrong here
Incorrect because DHCPv6 snooping requires separate configuration and is not enabled by default with DHCP snooping.
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 350-401 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 350-401 question test?
Infrastructure Security — This question tests Infrastructure Security — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: DHCP snooping is configured on Layer 2 switches to filter DHCP messages on untrusted ports. — DHCP snooping is a security feature that filters untrusted DHCP messages and builds a binding database. It is configured on switches, not routers. The DHCP snooping binding table contains the client MAC address, IP address, lease time, VLAN, and port. Trusted ports are typically uplinks to DHCP servers, while untrusted ports face clients. Option D is incorrect because the DHCP snooping database is stored in the switch's flash memory, not NVRAM. Option E is incorrect because DHCP snooping does not validate DHCPv6 messages by default; it is for DHCPv4 only unless DHCPv6 snooping is separately configured.
What should I do if I get this 350-401 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 350-401 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
About these practice questions
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Same concept, more angles
1 more ways this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which three statements about DHCP snooping are true? (Choose three.)
hard- ✓ A.DHCP snooping is configured on a per-VLAN basis.
- B.DHCP snooping prevents all types of ARP spoofing attacks.
- ✓ C.The DHCP snooping binding database includes the client MAC address, IP address, lease time, VLAN, and port.
- ✓ D.Ports connected to DHCP servers should be configured as trusted ports.
- E.DHCP snooping encrypts all DHCP traffic between the client and server.
Why A: DHCP snooping is a security feature that filters untrusted DHCP messages. It builds a DHCP snooping binding database from trusted sources. Option A is correct because DHCP snooping is typically enabled on VLANs, not globally on the switch. Option C is correct because the binding database contains the client MAC address, IP address, lease time, VLAN, and port. Option D is correct because ports connected to DHCP servers are configured as trusted to allow DHCP server messages. Option B is incorrect because DHCP snooping does not prevent all ARP spoofing; that is the role of Dynamic ARP Inspection (DAI). Option E is incorrect because DHCP snooping does not encrypt DHCP traffic; it only filters messages based on trust.
Last reviewed: Jun 18, 2026
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