Question 803 of 2,015

Infrastructure Security →mediumDrag & DropObjective-mapped

Quick Answer

The correct order is: intercept ARP packets on untrusted ports, check sender MAC and IP against the DHCP snooping binding table, validate ARP cache consistency, drop packets that mismatch, and finally forward valid ARP packets to the destination. This sequence is correct because Dynamic ARP Inspection (DAI) acts as a security guard for ARP traffic, first capturing all ARP packets arriving on ports designated as untrusted, then cross-referencing each packet’s source MAC and IP address against the trusted DHCP snooping database to detect spoofing attempts. On the ENCOR 350-401 exam, this drag-and-drop task tests your understanding of DAI’s role in preventing man-in-the-middle attacks, and a common trap is confusing the validation step with the forwarding step—remember that DAI drops invalid packets before it ever forwards a valid one. A helpful memory tip is “Intercept, Check, Validate, Drop, Forward,” or simply “ICVDF” for the five sequential actions.

350-401 Infrastructure Security Practice Question

This 350-401 practice question tests your understanding of infrastructure security. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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.

Drag and drop the steps of Dynamic ARP Inspection (DAI) packet validation into the correct order, from first to last.

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

Question 1mediumdrag order

Full question →

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

✓

Switch intercepts ARP request/reply on untrusted port

DAI first intercepts ARP packets on untrusted ports, then checks the sender MAC and IP against the DHCP snooping binding, validates ARP cache consistency, drops packets that mismatch, and finally forwards valid packets to the destination.

Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Common exam traps

Common exam trap: NAT rules depend on direction and matching traffic

NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.

Detailed technical explanation

How to think about this question

NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.

KKey Concepts to Remember

Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.

TExam Day Tips

Identify inside and outside interfaces first.
Check whether the scenario needs static NAT, dynamic NAT or PAT.
Do not confuse NAT matching ACLs with normal packet-filtering intent.

Key takeaway

NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.

Real-world example

How this comes up in practice

A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.

What to study next

Got this wrong? Here's your next step.

Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related 350-401 NAT questions on configuration and troubleshooting.

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FAQ

Questions learners often ask

What does this 350-401 question test?

Infrastructure Security — This question tests Infrastructure Security — Static NAT maps one inside address to one outside address..

What is the correct answer to this question?

The correct answer is: Switch intercepts ARP request/reply on untrusted port — DAI first intercepts ARP packets on untrusted ports, then checks the sender MAC and IP against the DHCP snooping binding, validates ARP cache consistency, drops packets that mismatch, and finally forwards valid packets to the destination.

What should I do if I get this 350-401 question wrong?

Are there clue words in this question I should notice?

Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

What is the key concept behind this question?

Static NAT maps one inside address to one outside address.

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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. Drag and drop the steps of Dynamic ARP Inspection (DAI) packet validation into the correct order, from first to last.

medium

✓ A.Enable DAI on specific VLANs
✓ B.Configure DHCP snooping binding table as validation source
✓ C.Switch receives ARP packet on untrusted port
✓ D.Compare sender MAC and IP against binding table
✓ E.Forward valid ARP or drop invalid packet

Why A: DAI validates ARP packets by first enabling it on VLANs, then using the DHCP snooping binding table as a source of truth. It checks the sender MAC and IP against the binding table and validates the packet format before forwarding or dropping.

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