CCNA Network Services and Security Practice Question
Dynamic ARP Inspection is most effective at preventing which attack?
⚠ Common exam trap
Be careful not to confuse ARP spoofing with other types of spoofing attacks like IP or DNS spoofing.
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
✓
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.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
SYN flood
Why it's wrong here
A SYN flood is a Denial-of-Service attack that exhausts a server's TCP connection resources by sending numerous SYN segments without completing the handshake, filling the listen backlog. DAI is not a stateful firewall; it inspects only ARP frames and does not analyze TCP flags, connection state, or session tables. Mitigating SYN floods requires techniques like SYN cookies, TCP intercept, or rate limiting on upstream firewalls and servers, not DAI.
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
Why this is correct
Dynamic ARP Inspection (DAI) is an L2 security feature that intercepts ARP packets on untrusted switch ports and verifies that the sender MAC and IP addresses match the DHCP snooping binding table. Any ARP response announcing a conflict or forged MAC-IP pairing—the defining characteristic of ARP spoofing—is dropped. By blocking these poisoned frames, DAI prevents an attacker from redirecting traffic to a rogue host for on-path interception or man-in-the-middle attacks.
- ✗
Route summarization error
Why it's wrong here
Route summarization is a routing protocol technique (used by EIGRP or OSPF) to aggregate contiguous network prefixes, reducing table size and update overhead. An error in summarization, such as creating an overly broad summary that includes discontiguous subnets, can cause packets to be blackholed or forwarded to the wrong destination. DAI examines only Layer 2 ARP messages exchanged within a VLAN and cannot influence or correct Layer 3 routing table construction, so it is irrelevant to summarization problems.
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
Why it's wrong here
A rogue DHCP relay injects DHCP relayed messages (such as DHCPOFFER or DHCPACK) into the network, potentially steering clients to a malicious DHCP server or corrupting address allocation. DAI's scope is limited to validating ARP packets against the DHCP snooping binding table; it does not parse DHCP relay agent information (option 82) nor control the forwarding behavior of DHCP messages. Protection against rogue DHCP relays relies on DHCP Snooping's port trust settings and rate limiting, not on DAI.
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
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.
✓ARP spoofingCorrect answer▾
Why this is correct
Dynamic ARP Inspection (DAI) is an L2 security feature that intercepts ARP packets on untrusted switch ports and verifies that the sender MAC and IP addresses match the DHCP snooping binding table. Any ARP response announcing a conflict or forged MAC-IP pairing—the defining characteristic of ARP spoofing—is dropped. By blocking these poisoned frames, DAI prevents an attacker from redirecting traffic to a rogue host for on-path interception or man-in-the-middle attacks.
✗SYN floodWrong answer — click to see why▾
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.
✗Route summarization errorWrong answer — click to see why▾
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.
✗Rogue DHCP relayWrong answer — click to see why▾
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?”
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
Related to this question
Learn chapter
RA Guard — IPv6 First-Hop Security
Key term
DHCP snooping
DHCP snooping is a network security feature that filters untrusted DHCP messages to prevent rogue DHCP servers from giving out false IP addresses.
Key term
Route summarization
Route summarization is a technique that combines multiple network routes into a single, more general route advertisement to reduce the size of routing tables and improve network performance.
About these practice questions
Courseiva writes every 200-301 question from scratch — 1,389 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.