- A
DAI validates ARP packets by checking the sender MAC and IP addresses against the DHCP snooping binding table.
Correct because DAI uses the DHCP snooping database to ensure ARP packets are legitimate.
- B
DAI can be configured on a per-VLAN basis using the 'ip arp inspection vlan' command.
Correct because DAI is enabled per VLAN with this global configuration command.
- C
DAI includes rate limiting to prevent ARP flooding attacks.
Correct because rate limiting is a built-in feature to mitigate ARP storms.
- D
DAI inspects both IPv4 ARP and IPv6 Neighbor Discovery packets.
Why wrong: Incorrect because DAI only works with IPv4 ARP; IPv6 uses ND and requires different mechanisms.
- E
DAI validates the destination IP address in ARP requests to prevent man-in-the-middle attacks.
Why wrong: Incorrect because DAI validates the sender MAC and IP, not the destination IP in requests.
Quick Answer
The correct answer is that DAI includes rate limiting to prevent ARP flooding attacks. Dynamic ARP Inspection validates ARP packets by cross-referencing the sender MAC and IP addresses against the DHCP snooping binding table, ensuring only legitimate ARP messages are forwarded. Rate limiting is a critical component of DAI because it throttles the number of ARP packets allowed per second on an interface, directly mitigating the risk of ARP storms or denial-of-service attacks that flood the network with spoofed ARP replies. On the ENCOR 350-401 exam, this concept often appears in a “choose three” format, where common traps include confusing DAI with IPv6 neighbor discovery or claiming it validates destination IPs in ARP requests. Remember that DAI is strictly for IPv4 ARP and only checks the sender’s hardware and protocol addresses. A useful memory tip: “DAI checks the sender, not the destination—and rate limits to prevent the flood.”
350-401 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 dynamic ARP inspection (DAI) 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
DAI validates ARP packets by checking the sender MAC and IP addresses against the DHCP snooping binding table.
Dynamic ARP Inspection (DAI) is a security feature that validates ARP packets in a network. It uses the DHCP snooping binding table to verify the MAC-to-IP address mapping. DAI is configured on a per-VLAN basis and can be applied to specific interfaces. Rate limiting is used to prevent ARP storms. Option D is incorrect because DAI does not inspect ARP replies for IPv6; it is for IPv4 ARP only. Option E is incorrect because DAI does not validate the destination IP address of ARP requests; it validates the sender MAC and IP in the ARP body.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
DAI validates ARP packets by checking the sender MAC and IP addresses against the DHCP snooping binding table.
Why this is correct
Correct because DAI uses the DHCP snooping database to ensure ARP packets are legitimate.
Related concept
OSPF neighbours must agree on key parameters.
- ✓
DAI can be configured on a per-VLAN basis using the 'ip arp inspection vlan' command.
- ✓
DAI includes rate limiting to prevent ARP flooding attacks.
- ✗
DAI inspects both IPv4 ARP and IPv6 Neighbor Discovery packets.
- ✗
DAI validates the destination IP address in ARP requests to prevent man-in-the-middle attacks.
Why it's wrong here
Incorrect because DAI validates the sender MAC and IP, not the destination IP in requests.
Common exam traps
Common exam trap: OSPF can fail even when IP connectivity looks correct
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
How to think about this question
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
KKey Concepts to Remember
- OSPF neighbours must agree on key parameters.
- Router ID selection can affect neighbour relationships and LSDB output.
- OSPF cost influences the preferred path.
- A route can appear in OSPF information but not become the installed route.
TExam Day Tips
- Check area mismatch first when OSPF adjacency fails.
- Review passive interfaces when a network is advertised but no neighbour forms.
- Use show ip ospf neighbor and show ip route clues carefully.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
How this comes up in practice
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Got this wrong? Here's your next step.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.
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FAQ
Questions learners often ask
What does this 350-401 question test?
Infrastructure Security — This question tests Infrastructure Security — OSPF neighbours must agree on key parameters..
What is the correct answer to this question?
The correct answer is: DAI validates ARP packets by checking the sender MAC and IP addresses against the DHCP snooping binding table. — Dynamic ARP Inspection (DAI) is a security feature that validates ARP packets in a network. It uses the DHCP snooping binding table to verify the MAC-to-IP address mapping. DAI is configured on a per-VLAN basis and can be applied to specific interfaces. Rate limiting is used to prevent ARP storms. Option D is incorrect because DAI does not inspect ARP replies for IPv6; it is for IPv4 ARP only. Option E is incorrect because DAI does not validate the destination IP address of ARP requests; it validates the sender MAC and IP in the ARP body.
What should I do if I get this 350-401 question wrong?
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 350-401 OSPF questions on adjacency and route selection.
What is the key concept behind this question?
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 18, 2026
This 350-401 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 350-401 exam.
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