Quick Answer
The answer is Dynamic ARP Inspection. This switch security feature is the correct choice because it uses DHCP snooping bindings as a trusted source of truth to validate ARP packets, comparing the source MAC and IP addresses in each ARP message against the binding table. If an ARP packet contains mismatched information—such as a forged source IP claiming a different MAC—DAI drops the packet, effectively stopping ARP spoofing attacks at the access layer. On the CCNA 200-301 v2 exam, this question tests your understanding of how Layer 2 security features work together; a common trap is confusing DAI with DHCP snooping itself, but remember that DHCP snooping builds the database, while DAI is the enforcement mechanism that checks ARP traffic against it. For a quick memory tip, think “DAI checks ARP, DHCP snooping builds the map”—the two are inseparable partners in preventing man-in-the-middle spoofing.
This 200-301 practice question tests your understanding of network services and security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches.. 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 switch security feature uses DHCP snooping bindings to validate ARP packets and help stop ARP spoofing?
PortFast
Why wrong: PortFast is used for fast edge-port transition, not ARP validation.
Dynamic ARP Inspection
Correct. DAI is designed to mitigate ARP spoofing.
UDLD
Why wrong: UDLD addresses unidirectional link problems, not ARP spoofing.
HSRP preemption
Why wrong: HSRP preemption concerns first-hop redundancy.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Dynamic ARP Inspection
Dynamic ARP Inspection compares ARP information to trusted bindings, often learned through DHCP snooping, to block forged ARP packets.
Key principle: Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
PortFast
When this WOULD be correct
If the question asked about features that enhance the speed of port activation or reduce network downtime during link changes, PortFast would be the correct answer. For example, a question might ask which feature enables faster connectivity for end devices in a network.
Dynamic ARP Inspection
Related concept
Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches.
UDLD
Why it's wrong here
UDLD addresses unidirectional link problems, not ARP spoofing.
When this WOULD be correct
If the question asked about a feature that detects and mitigates unidirectional links or loops in a network, such as 'Which feature helps identify unidirectional links to prevent network issues?', then UDLD would be the correct answer.
HSRP preemption
Why it's wrong here
HSRP preemption concerns first-hop redundancy.
When this WOULD be correct
If the question asked about features related to router redundancy and failover mechanisms, specifically in the context of HSRP, then HSRP preemption would be the correct answer. For example, a question could ask which feature allows a backup router to regain active status when it becomes the highest priority router.
Option-by-option analysis
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.
Why this is correct
Correct. DAI is designed to mitigate ARP spoofing.
Why this is wrong here
PortFast is a spanning-tree feature that immediately transitions a port to forwarding state, bypassing the listening and learning states. It does not inspect ARP packets or use DHCP snooping bindings, so it cannot prevent ARP spoofing.
★ When this WOULD be the correct answer
If the question asked about features that enhance the speed of port activation or reduce network downtime during link changes, PortFast would be the correct answer. For example, a question might ask which feature enables faster connectivity for end devices in a network.
Why candidates choose this
Students might confuse PortFast with security features because it is often enabled on access ports for faster connectivity, but its purpose is unrelated to ARP validation.
Why this is wrong here
UDLD (Unidirectional Link Detection) is a protocol that detects and disables unidirectional links, which occur when traffic flows in one direction only. It does not inspect ARP packets or use DHCP snooping bindings, so it is not designed to stop ARP spoofing.
★ When this WOULD be the correct answer
If the question asked about a feature that detects and mitigates unidirectional links or loops in a network, such as 'Which feature helps identify unidirectional links to prevent network issues?', then UDLD would be the correct answer.
Why candidates choose this
UDLD sounds like a security feature because it detects link issues, but its focus is on physical layer problems, not ARP validation.
Why this is wrong here
HSRP preemption is a feature of the Hot Standby Router Protocol that allows a higher-priority router to take over as the active router. It does not inspect ARP packets or use DHCP snooping bindings, so it cannot prevent ARP spoofing.
★ When this WOULD be the correct answer
If the question asked about features related to router redundancy and failover mechanisms, specifically in the context of HSRP, then HSRP preemption would be the correct answer. For example, a question could ask which feature allows a backup router to regain active status when it becomes the highest priority router.
Why candidates choose this
Students might associate HSRP with security because it provides redundancy, but preemption is about router role assignment, not ARP validation.
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
A common exam trap is selecting PortFast, UDLD, or HSRP preemption as the answer because these features are well-known switch security or stability mechanisms. However, PortFast only speeds up STP port transitions and does not inspect ARP packets. UDLD focuses on detecting unidirectional links and does not validate ARP traffic. HSRP preemption deals with gateway redundancy and has no role in ARP security. The key to avoiding this trap is recognizing that only Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and stop ARP spoofing.
Detailed technical explanation
Dynamic ARP Inspection (DAI) is a security feature implemented on Cisco switches to prevent ARP spoofing attacks. ARP spoofing occurs when a malicious device sends forged ARP messages onto a LAN, associating its MAC address with the IP address of another host, which can lead to man-in-the-middle attacks or denial of service. DAI works by intercepting all ARP packets on untrusted ports and validating them against a trusted database of IP-to-MAC bindings, typically learned through DHCP snooping. This ensures only legitimate ARP requests and replies are forwarded, blocking any forged or malicious ARP packets. The validation process in DAI relies heavily on DHCP snooping bindings, which record the IP address, MAC address, lease time, binding type, VLAN, and interface of DHCP clients. When an ARP packet is received, DAI compares the sender's IP and MAC addresses against the DHCP snooping table. If the packet does not match a valid binding or comes from an untrusted port, DAI drops the packet. This mechanism effectively stops ARP spoofing by ensuring that only ARP packets with valid IP-MAC mappings are allowed, protecting the integrity of the Layer 2 network. A common exam trap is confusing DAI with other security features like PortFast, UDLD, or HSRP preemption. PortFast accelerates STP convergence but does not validate ARP packets. UDLD detects unidirectional links but does not inspect ARP traffic. HSRP preemption manages first-hop redundancy and does not provide ARP security. Understanding that DAI specifically uses DHCP snooping bindings to validate ARP packets is critical for correctly answering questions about switch security features that prevent ARP spoofing.
Key takeaway
Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches.
Real-world example
A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Review dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Services and Security — This question tests Network Services and Security — Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches..
The correct answer is: Dynamic ARP Inspection — Dynamic ARP Inspection compares ARP information to trusted bindings, often learned through DHCP snooping, to block forged ARP packets.
Review dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches., then practise related 200-301 questions on the same topic to reinforce the concept.
Dynamic ARP Inspection uses DHCP snooping bindings to validate ARP packets and prevent ARP spoofing attacks on Cisco switches.
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Last reviewed: May 17, 2026
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