- A
It filters IPv6 traffic based on the source IPv6 address of incoming packets.
IPv6 Source Guard checks the source address against the binding table and drops packets with invalid source addresses.
- B
It relies on the IPv6 snooping binding table, which is populated by DHCPv6 snooping or ND Inspection.
The binding table is built from DHCPv6 snooping entries or ND Inspection, and Source Guard uses this table to validate traffic.
- C
It can be configured to allow traffic from specific prefixes using a static prefix list.
A static prefix list can be applied to permit traffic from certain prefixes, overriding dynamic entries.
- D
It filters both incoming and outgoing IPv6 traffic on a port.
Why wrong: IPv6 Source Guard filters only incoming traffic (ingress) to prevent spoofing; it does not filter outgoing traffic.
- E
It requires DHCPv6 snooping to be enabled on the VLAN to function.
Why wrong: While DHCPv6 snooping can populate the binding table, ND Inspection can also be used; DHCPv6 snooping is not strictly required.
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 THREE statements about IPv6 Source Guard 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
It filters IPv6 traffic based on the source IPv6 address of incoming packets.
Option A is correct because IPv6 Source Guard filters incoming IPv6 traffic on a per-port basis by examining the source IPv6 address of packets and comparing it against the IPv6 snooping binding table. If the source address does not match a valid binding, the packet is dropped, preventing spoofing attacks.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It filters IPv6 traffic based on the source IPv6 address of incoming packets.
Why this is correct
IPv6 Source Guard checks the source address against the binding table and drops packets with invalid source addresses.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
It relies on the IPv6 snooping binding table, which is populated by DHCPv6 snooping or ND Inspection.
Why this is correct
The binding table is built from DHCPv6 snooping entries or ND Inspection, and Source Guard uses this table to validate traffic.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
It can be configured to allow traffic from specific prefixes using a static prefix list.
Why this is correct
A static prefix list can be applied to permit traffic from certain prefixes, overriding dynamic entries.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
It filters both incoming and outgoing IPv6 traffic on a port.
Why it's wrong here
IPv6 Source Guard filters only incoming traffic (ingress) to prevent spoofing; it does not filter outgoing traffic.
- ✗
It requires DHCPv6 snooping to be enabled on the VLAN to function.
Why it's wrong here
While DHCPv6 snooping can populate the binding table, ND Inspection can also be used; DHCPv6 snooping is not strictly required.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that IPv6 Source Guard filters both inbound and outbound traffic, when in fact it only filters inbound traffic, and the trap here is assuming DHCPv6 snooping is mandatory when ND Inspection can also supply the binding table.
Detailed technical explanation
How to think about this question
IPv6 Source Guard leverages the IPv6 snooping binding table, which is built from DHCPv6 snooping or ND Inspection messages (e.g., Neighbor Advertisements and Router Advertisements). When a packet arrives on a port, the switch performs a lookup in this binding table; if the source IPv6 address is not found or is invalid, the packet is discarded. In real-world deployments, this prevents rogue IPv6 devices from using forged source addresses to bypass access controls or launch man-in-the-middle attacks.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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
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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 — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It filters IPv6 traffic based on the source IPv6 address of incoming packets. — Option A is correct because IPv6 Source Guard filters incoming IPv6 traffic on a per-port basis by examining the source IPv6 address of packets and comparing it against the IPv6 snooping binding table. If the source address does not match a valid binding, the packet is dropped, preventing spoofing attacks.
What should I do if I get this 300-410 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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