- A
Enable IPv6 ND snooping on the VLAN to allow the switch to learn the host's binding from Neighbor Discovery messages.
Correct because ND snooping creates bindings for static addresses, allowing IPv6 Source Guard to permit traffic.
- B
Configure the host to use DHCPv6 to obtain an address so that the binding is learned via DHCPv6 snooping.
Why wrong: Incorrect because while DHCPv6 snooping would create a binding, the host is using a static address; changing the host configuration may not be desirable.
- C
Add a static binding entry for the host in the IPv6 binding table using the 'ipv6 neighbor' command.
Why wrong: Incorrect because the 'ipv6 neighbor' command adds an entry to the switch's neighbor cache, not to the IPv6 Source Guard binding table; the binding table is populated by snooping.
- D
Disable IPv6 Source Guard on the port connected to the host.
Why wrong: Incorrect because the question asks to resolve the issue without disabling IPv6 Source Guard.
300-410 IPv6 First Hop Security Practice Question
This 300-410 practice question tests your understanding of ipv6 first hop security. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A network engineer is troubleshooting an issue where IPv6 traffic from a host is being dropped by the switch. The switch has IPv6 Source Guard enabled. The host has a static IPv6 address 2001:db8:2::20. The engineer sees that the binding table does not contain an entry for this host. What should the engineer do to resolve the issue without disabling IPv6 Source Guard?
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
Enable IPv6 ND snooping on the VLAN to allow the switch to learn the host's binding from Neighbor Discovery messages.
IPv6 Source Guard relies on the IPv6 binding table to validate traffic. When a host uses a static IPv6 address, the switch cannot learn the binding via DHCPv6 snooping. Enabling IPv6 ND snooping on the VLAN allows the switch to inspect Neighbor Discovery (ND) messages (RFC 4861) and dynamically populate the binding table with the host's IPv6 address and MAC address, thus permitting the traffic without disabling Source Guard.
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.
- ✓
Enable IPv6 ND snooping on the VLAN to allow the switch to learn the host's binding from Neighbor Discovery messages.
Why this is correct
Correct because ND snooping creates bindings for static addresses, allowing IPv6 Source Guard to permit traffic.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Configure the host to use DHCPv6 to obtain an address so that the binding is learned via DHCPv6 snooping.
Why it's wrong here
Incorrect because while DHCPv6 snooping would create a binding, the host is using a static address; changing the host configuration may not be desirable.
- ✗
Add a static binding entry for the host in the IPv6 binding table using the 'ipv6 neighbor' command.
Why it's wrong here
Incorrect because the 'ipv6 neighbor' command adds an entry to the switch's neighbor cache, not to the IPv6 Source Guard binding table; the binding table is populated by snooping.
- ✗
Disable IPv6 Source Guard on the port connected to the host.
Why it's wrong here
Incorrect because the question asks to resolve the issue without disabling IPv6 Source Guard.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between the IPv6 neighbor cache (Layer 2 mapping) and the IPv6 binding table (used by First Hop Security features), leading candidates to mistakenly choose the 'ipv6 neighbor' command as a solution for Source Guard bindings.
Trap categories for this question
Command / output trap
Incorrect because the 'ipv6 neighbor' command adds an entry to the switch's neighbor cache, not to the IPv6 Source Guard binding table; the binding table is populated by snooping.
Detailed technical explanation
How to think about this question
IPv6 ND snooping works by monitoring Neighbor Solicitation (NS) and Neighbor Advertisement (NA) messages to build a binding of IPv6 addresses to MAC addresses on a per-port basis. This binding table is then used by IPv6 Source Guard to filter traffic, dropping packets whose source IPv6 address does not match a learned or statically configured binding. In real-world deployments, hosts with static IPv6 addresses are common in server or management networks, making ND snooping essential for Source Guard to function without DHCPv6.
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 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.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
What to study next
Got this wrong? Here's your next step.
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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: Enable IPv6 ND snooping on the VLAN to allow the switch to learn the host's binding from Neighbor Discovery messages. — IPv6 Source Guard relies on the IPv6 binding table to validate traffic. When a host uses a static IPv6 address, the switch cannot learn the binding via DHCPv6 snooping. Enabling IPv6 ND snooping on the VLAN allows the switch to inspect Neighbor Discovery (ND) messages (RFC 4861) and dynamically populate the binding table with the host's IPv6 address and MAC address, thus permitting the traffic without disabling Source Guard.
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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