Question 138 of 2,152

IPv6 First Hop Security →hardMultiple SelectObjective-mapped

300-410 IPv6 First Hop Security Practice Question

This 300-410 practice question tests your understanding of ipv6 first hop 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.

Which TWO statements about IPv6 First Hop Security (FHS) Source Guard are true? (Choose TWO.)

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 1hardmulti select

Study the full IPv6 explanation →

A
IPv6 Source Guard dynamically creates binding entries for all IPv6 addresses learned via ND.
Why wrong: Incorrect. Source Guard does not create bindings; it relies on DHCPv6 snooping or ND snooping to populate the binding table.
B
IPv6 Source Guard uses the IPv6 binding table to permit or deny traffic based on source address.
Correct. Source Guard checks the source IPv6 address and MAC against the binding table and drops unauthorized traffic.
C
IPv6 Source Guard filters traffic based on the destination IPv6 address in the packet.
Why wrong: Incorrect. Source Guard filters based on source address, not destination.
D
IPv6 Source Guard can be enabled on a per-interface or per-VLAN basis.
Correct. The 'ipv6 source-guard' command can be applied to an interface or a VLAN.
E
IPv6 Source Guard only works with addresses learned via DHCPv6.
Why wrong: Incorrect. It can also work with addresses learned via ND snooping, not just DHCPv6.

Full breakdown with real-world context →

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

✓

IPv6 Source Guard uses the IPv6 binding table to permit or deny traffic based on source address.

IPv6 Source Guard filters traffic based on the source IPv6 address and MAC address, using the binding table. It can be used with both SLAAC and DHCPv6, but it does not create bindings itself—it relies on DHCPv6 snooping or ND snooping. Option B is correct because Source Guard uses the binding table to validate source addresses. Option D is correct because Source Guard can be enabled per interface or per VLAN. Option A is incorrect because Source Guard does not create bindings; it uses bindings from DHCPv6 snooping or ND snooping. Option C is incorrect because Source Guard filters on source IP and MAC, not destination. Option E is incorrect because Source Guard is not limited to DHCPv6-learned addresses; it can also use ND snooping entries.

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.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✗
IPv6 Source Guard dynamically creates binding entries for all IPv6 addresses learned via ND.
Why it's wrong here
Incorrect. Source Guard does not create bindings; it relies on DHCPv6 snooping or ND snooping to populate the binding table.
✓
IPv6 Source Guard uses the IPv6 binding table to permit or deny traffic based on source address.
Why this is correct
Correct. Source Guard checks the source IPv6 address and MAC against the binding table and drops unauthorized traffic.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
IPv6 Source Guard filters traffic based on the destination IPv6 address in the packet.
Why it's wrong here
Incorrect. Source Guard filters based on source address, not destination.
✓
IPv6 Source Guard can be enabled on a per-interface or per-VLAN basis.
Why this is correct
Correct. The 'ipv6 source-guard' command can be applied to an interface or a VLAN.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
IPv6 Source Guard only works with addresses learned via DHCPv6.
Why it's wrong here
Incorrect. It can also work with addresses learned via ND snooping, not just DHCPv6.

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 300-410 questions on switching, trunking, and access-port configuration.

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FAQ

Questions learners often ask

What does this 300-410 question test?

IPv6 First Hop Security — This question tests IPv6 First Hop Security — Access ports place end devices into a single VLAN..

What is the correct answer to this question?

The correct answer is: IPv6 Source Guard uses the IPv6 binding table to permit or deny traffic based on source address. — IPv6 Source Guard filters traffic based on the source IPv6 address and MAC address, using the binding table. It can be used with both SLAAC and DHCPv6, but it does not create bindings itself—it relies on DHCPv6 snooping or ND snooping. Option B is correct because Source Guard uses the binding table to validate source addresses. Option D is correct because Source Guard can be enabled per interface or per VLAN. Option A is incorrect because Source Guard does not create bindings; it uses bindings from DHCPv6 snooping or ND snooping. Option C is incorrect because Source Guard filters on source IP and MAC, not destination. Option E is incorrect because Source Guard is not limited to DHCPv6-learned addresses; it can also use ND snooping entries.

What should I do if I get this 300-410 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.

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