What Is the Purpose of IPv6 Snooping?

300-410 By islever Editorial Last updated

Describe IPv6 First Hop security features (RA guard, DHCP guard, binding table, ND inspection/snooping, source guard)

Short answer

D IPv6 snooping inspects ND and DHCPv6 control traffic on the Layer 2 port to build the First-Hop Security binding table.

Question

What is the use of IPv6 snooping?
  1. captures IPv6 routing protocol packets to analyze
  2. requires an external IPv6 packet analyzer
  3. required for the operation of IPv6 RA Guard
  4. captures any type of user traffic to create a binding table Correct Answer

Key Takeaways

You are tested on the purpose of IPv6 snooping, which is populating the First-Hop Security binding table from IPv6 control traffic, while the trap is option C, which wrongly implies RA Guard cannot operate without snooping.

IPv6 snooping is a First-Hop Security feature that inspects Neighbor Discovery and DHCPv6 messages on a Layer 2 port to build the IPv6 binding table. This page explains why option D — creating that binding table — is the intended answer on 300-410, and why RA Guard (option C) is the classic trap.

Common mistake: Most candidates choose C, assuming IPv6 snooping must be enabled for RA Guard to work; RA Guard is enforced by its own device-role policy, and snooping's defining job is building the address/MAC/port binding table, so D is the intended answer.

Expert Analysis

Why the Answer Is Correct

IPv6 snooping (also called IPv6 Neighbor Discovery inspection) is a First-Hop Security feature that runs on the Layer 2 switch port and inspects IPv6 control traffic such as Neighbor Discovery and DHCPv6 messages to learn and populate the binding table of IPv6 address, MAC address and port. That table is the foundation other FHS features use to drop spoofed or unauthorized messages, such as bogus Router Advertisements or rogue DHCPv6 replies. Option D, "captures any type of user traffic to create a binding table," is the only choice that names that purpose, which is why every recorded vote lands on D. The wording of D is admittedly loose, because the table is fed by ND and DHCPv6 messages rather than literally every packet a user sends, but as Pietjeplukgeluk noted it remains the best of all options. On 300-410 the exam expects you to recognize the purpose (build the binding table), not to defend Cisco's phrasing.

Why the Other Options Are Wrong

Option A is wrong because IPv6 snooping is not a capture-and-analyze tool for routing protocols such as OSPFv3 or RIPng; embedded packet capture or a SPAN session serves that need. Option B is wrong for the same reason: the feature is inline on the switch and needs no external IPv6 packet analyzer to function. Option C is the strongest distractor because RA Guard and snooping are both First-Hop Security features and are frequently deployed together, but RA Guard is enforced by its own policy with a device role of host or router and does not depend on snooping for its operation. The question asks what snooping is for, and that answer is the binding table, not RA Guard.

Community Comment Notes

TonyTe0 gives the cleanest paraphrase of the feature, writing that IPv6 snooping "captures the IPv6 traffic and helps in populating the binding table" from NDP or DHCP packets, and that it also blocks unwanted messages. Brahim90 cites a Cisco book page describing ND inspection as placing valid bindings in the table and dropping messages that lack valid bindings, which matches the exam's intent. Pietjeplukgeluk and dapardo back D while cautioning that snooping does not capture literally any traffic, only the control messages that feed the table. amir_lotfy voted C and argued that RA Guard relies on snooping to inspect Router Advertisements, which is precisely the trap this question is built around.

Exam Strategy

Treat this as a purpose question: read the four options and eliminate anything that describes a capture/analyzer tool (A and B) or the dependency of another feature (C). If you can recall that the IPv6 binding table on a Layer 2 port is populated by snooping ND and DHCPv6 messages, the answer falls out immediately.

Frequently Asked Questions

Why is option C (RA Guard requires IPv6 snooping) not the answer?

RA Guard is enforced by its own device-role policy and filters RAs independently; the question asks what snooping itself is for, and that is building the binding table.

Does IPv6 snooping really capture "any type of user traffic"?

No, it snoops IPv6 control traffic such as Neighbor Discovery and DHCPv6 messages to create address, MAC and port bindings; option D is simply the closest wording available.

More 300-410 FAQ →

Community Votes

D
100%

100% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 6 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 6

  1. TonyTe0 👍 2
    D: correct IPv6 Snooping IPv6 snooping captures the IPv6 traffic and helps in populating the binding table. It gathers addresses in control messages such as Neighbor Discovery Protocol (NDP) or Dynamic Host Configuration Protocol (DHCP) packets. Depending on the security level, it blocks unwanted messages such as Router Advertisements (RA) or DHCP replies. This feature is a pre-requisite to the remaining security features mentioned here. https://www.cisco.com/c/en/us/td/docs/routers/7600/ios/15S/configuration/guide/7600_15_0s_book/IPv6_Security.html
  2. bk989 👍 2
    A: Obviously it doesn't inspect OSPF packets. Any type of layer 3 pakets are DHCP packets. FALSE B:No it doesn't. This isn't the point of IPv6 snooping, it's for IPv6 security on the switch. C: According to the link I provided C is false (see below) D: By capturing any type of user traffic: ND packets, DHCP packets, and some data packets I guess this is the answer.
  3. Pietjeplukgeluk 👍 2 Answered D
    D is wrong answer, but the best of all options as it does NOT capture "ANY" traffic, it only capture DHCPV6 traffic to create binding table entries
  4. Brahim90 👍 1 Answered D
    Given answer is correct per cisco book page 864. IPv6 Neighbor Discovery Inspection/IPv6 Snooping IPv6 neighbor discovery inspection/snooping is a feature that learns and populates the binding table for stateless autoconfiguration addresses. It analyzes ND (neighbor discovery) messages and places valid bindings in the binding table and drops all messages that do not have valid bindings. A valid ND message is one where the IPv6-to-MAC mapping can be verified.
  5. amir_lotfy 👍 1 Answered C
    IPv6 Snooping Enabled: IPv6 RA Guard relies on IPv6 snooping to inspect and filter IPv6 Router Advertisement (RA) messages received on Layer 2 interfaces. Therefore, IPv6 snooping must be enabled on the switch where RA Guard is configured.
Show 1 more comment
  1. dapardo 👍 2 Answered D
    Agree on TonyTe0 explanation

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