Question 107 of 2,015

NAT and DHCP →mediumDrag & DropObjective-mapped

Quick Answer

The correct order ends with valid ARP packets being forwarded and invalid ARP packets being dropped. This sequence is correct because DHCP snooping must first build a reliable binding table by monitoring DHCP messages exchanged between clients and servers, validating server messages only on trusted ports to block rogue DHCP offers. Once that binding table is established, Dynamic ARP Inspection (DAI) can then intercept every ARP packet on untrusted ports and cross-reference the sender’s MAC and IP address against the table. If the ARP packet matches a valid binding, it is forwarded; if it does not match or is inconsistent, it is dropped. On the ENCOR 350-401 exam, this drag-and-drop task tests your understanding of the causal dependency between DHCP snooping and DAI—a common trap is placing DAI steps before the binding table is built. Remember the memory tip: “Bind first, then inspect—match forwards, mismatch rejects.”

350-401 NAT and DHCP Practice Question

This 350-401 practice question tests your understanding of nat and dhcp. 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 DHCP snooping and dynamic ARP inspection flow 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

Read the full DHCP explanation →

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 enables DHCP snooping globally and per VLAN

DHCP snooping first builds a binding table by monitoring DHCP messages. The switch validates DHCP server messages on trusted ports and discards rogue offers. For DAI, the switch intercepts ARP packets and checks the sender MAC and IP against the DHCP snooping binding table. If the ARP packet matches, it is forwarded; otherwise, it is dropped.

Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

Common exam traps

Common exam trap: an active trunk can still block the VLAN you need

A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.

Detailed technical explanation

How to think about this question

VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.

KKey Concepts to Remember

Access ports place end devices into a single VLAN.
Trunk ports carry multiple VLANs between switches.
Allowed VLAN lists decide which VLANs can cross a trunk.
Native VLAN mismatch can create confusing symptoms.

TExam Day Tips

Use show vlan brief to verify access VLANs.
Use show interfaces trunk to verify trunk state and allowed VLANs.
Do not treat every same-VLAN issue as a routing problem.

Key takeaway

A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.

Real-world example

How this comes up in practice

A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.

What to study next

Got this wrong? Here's your next step.

Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 350-401 questions on switching, trunking, and access-port configuration.

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FAQ

Questions learners often ask

What does this 350-401 question test?

NAT and DHCP — This question tests NAT and DHCP — Access ports place end devices into a single VLAN..

What is the correct answer to this question?

The correct answer is: Switch enables DHCP snooping globally and per VLAN — DHCP snooping first builds a binding table by monitoring DHCP messages. The switch validates DHCP server messages on trusted ports and discards rogue offers. For DAI, the switch intercepts ARP packets and checks the sender MAC and IP against the DHCP snooping binding table. If the ARP packet matches, it is forwarded; otherwise, it is dropped.

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?

Access ports place end devices into a single VLAN.

About these practice questions

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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 DHCP snooping and dynamic ARP inspection flow into the correct order, from first to last.

medium

✓ A.Switch enables DHCP snooping on trusted ports
✓ B.Switch intercepts DHCPACK from server, extracts lease info
✓ C.Switch populates DHCP snooping binding table
✓ D.Switch receives ARP packet on untrusted port
✓ E.Switch validates ARP against binding table, drops if mismatch

Why A: DHCP snooping builds a binding table used by DAI. The switch validates DHCP messages, creates bindings, then intercepts ARP packets and compares them against the binding table to prevent spoofing.

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