Quick Answer
The answer is ARP spoofing. Dynamic ARP Inspection (DAI) prevents this attack by validating ARP packets on a per-interface basis against a trusted database built by DHCP snooping, dropping any invalid ARP replies that attempt to associate a different MAC address with an existing IP address. On the CCNA 200-301 v2 exam, this concept tests your understanding of Layer 2 security mechanisms and how DAI specifically targets ARP poisoning, not other threats like SYN floods (Layer 4) or rogue DHCP relays (handled by DHCP snooping). A common trap is confusing DAI with DHCP snooping—remember that DAI protects the ARP table, while DHCP snooping protects the DHCP lease process. A helpful memory tip: DAI stops the “spoof,” so think “DAI = Drops ARP Impersonation.”
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. A key principle to apply: dynamic ARP Inspection validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks.. 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.
Dynamic ARP Inspection is most effective at preventing which attack?
SYN flood
Why wrong: DAI does not inspect TCP session setup behavior.
ARP spoofing
Correct. DAI is designed to stop forged ARP information.
Route summarization error
Why wrong: That is a routing design issue, not an ARP attack.
Rogue DHCP relay
Why wrong: DAI does not function as DHCP relay control.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ARP spoofing
Dynamic ARP Inspection (DAI) validates ARP packets on a per-interface basis, dropping invalid ARP replies and thus preventing ARP spoofing and poisoning attacks. Option A (SYN flood) is a Layer 4 TCP attack mitigated by TCP flood protection or SYN cookies, not DAI. Option C (route summarization error) is a routing misconfiguration unrelated to ARP security. Option D (rogue DHCP relay) is prevented by DHCP snooping, which works alongside DAI but DAI itself does not block rogue DHCP relays.
Key principle: Dynamic ARP Inspection validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
SYN flood
When this WOULD be correct
If the question were to ask about a security mechanism that protects against various types of DoS attacks, including SYN floods, then this option could be correct. For example, a question might focus on overall network security measures that mitigate multiple attack vectors, including SYN floods.
ARP spoofing
Related concept
Dynamic ARP Inspection validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks.
Route summarization error
Why it's wrong here
That is a routing design issue, not an ARP attack.
When this WOULD be correct
If the exam question asked about the effectiveness of security measures in preventing routing protocol misconfigurations or errors, then a focus on route summarization could be relevant. For example, a question could ask which method helps prevent routing loops caused by incorrect summarization.
Rogue DHCP relay
When this WOULD be correct
If the exam question asked about security measures to prevent unauthorized DHCP servers from distributing IP addresses in a network, then 'Rogue DHCP relay' would be the correct answer. This would focus on DHCP snooping or similar technologies rather than ARP-related protections.
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 stop forged ARP information.
Why this is wrong here
A SYN flood attack targets the TCP layer by overwhelming a server with connection requests, which is unrelated to ARP operations. Dynamic ARP Inspection specifically addresses issues at the link layer, making this option incorrect for the question asked.
★ When this WOULD be the correct answer
If the question were to ask about a security mechanism that protects against various types of DoS attacks, including SYN floods, then this option could be correct. For example, a question might focus on overall network security measures that mitigate multiple attack vectors, including SYN floods.
Why candidates choose this
Candidates may confuse ARP-related security measures with general network security concepts, leading them to mistakenly associate SYN floods with ARP Inspection due to a lack of clarity on the specific functions of each security mechanism.
Why this is wrong here
Route summarization error pertains to the aggregation of IP address ranges in routing protocols, which is unrelated to ARP operations. Dynamic ARP Inspection specifically targets ARP spoofing, not routing issues.
★ When this WOULD be the correct answer
If the exam question asked about the effectiveness of security measures in preventing routing protocol misconfigurations or errors, then a focus on route summarization could be relevant. For example, a question could ask which method helps prevent routing loops caused by incorrect summarization.
Why candidates choose this
Candidates may confuse ARP-related security with routing issues due to overlapping knowledge areas in networking, leading them to mistakenly associate route summarization with ARP protection.
Why this is wrong here
Rogue DHCP relay attacks involve unauthorized DHCP servers assigning IP addresses, which Dynamic ARP Inspection does not specifically address. This option is incorrect as it does not relate to ARP traffic manipulation.
★ When this WOULD be the correct answer
If the exam question asked about security measures to prevent unauthorized DHCP servers from distributing IP addresses in a network, then 'Rogue DHCP relay' would be the correct answer. This would focus on DHCP snooping or similar technologies rather than ARP-related protections.
Why candidates choose this
Candidates may confuse DHCP-related attacks with ARP-related protections due to their overlapping roles in network security, leading them to mistakenly believe that Dynamic ARP Inspection could mitigate DHCP issues.
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
Be careful not to confuse ARP spoofing with other types of spoofing attacks like IP or DNS spoofing.
Detailed technical explanation
Dynamic ARP Inspection (DAI) is a security feature used in Cisco networks to prevent ARP spoofing attacks by validating ARP packets on untrusted Layer 2 ports. ARP spoofing involves an attacker sending forged ARP messages to associate their MAC address with the IP address of another host, enabling man-in-the-middle attacks or denial of service. DAI intercepts ARP requests and replies, comparing them against a trusted database, typically built from DHCP snooping bindings, to ensure only valid ARP traffic is forwarded. DAI operates by inspecting ARP packets on access ports and verifying that the MAC-to-IP bindings match the entries in the DHCP snooping binding table or static entries. If an ARP packet fails validation, DAI drops it, effectively blocking forged ARP messages. This mechanism is specifically designed to prevent ARP spoofing and poisoning attacks, which are common threats in switched LAN environments. Other attacks like SYN floods or routing errors are outside DAI’s scope because they target different protocol layers or functions. A common exam trap is confusing DAI’s function with protections against other types of attacks such as SYN floods or DHCP relay attacks. While DAI secures ARP traffic, it does not inspect TCP session setups or control DHCP relay behavior. Understanding that DAI’s role is limited to ARP packet validation helps avoid selecting incorrect answers related to unrelated attack types. In practical networks, enabling DAI on access switches enhances LAN security by preventing attackers from poisoning the ARP cache and intercepting traffic.
Key takeaway
Dynamic ARP Inspection validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks.
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 validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks. 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 validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks., 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 validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks..
The correct answer is: ARP spoofing — Dynamic ARP Inspection (DAI) validates ARP packets on a per-interface basis, dropping invalid ARP replies and thus preventing ARP spoofing and poisoning attacks. Option A (SYN flood) is a Layer 4 TCP attack mitigated by TCP flood protection or SYN cookies, not DAI. Option C (route summarization error) is a routing misconfiguration unrelated to ARP security. Option D (rogue DHCP relay) is prevented by DHCP snooping, which works alongside DAI but DAI itself does not block rogue DHCP relays.
Review dynamic ARP Inspection validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks., then practise related 200-301 questions on the same topic to reinforce the concept.
Dynamic ARP Inspection validates ARP packets by comparing them against trusted MAC-to-IP bindings to prevent ARP spoofing attacks on Layer 2 networks.
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Last reviewed: May 17, 2026
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