What Is the Purpose of DHCPv6 Guard?
What is the purpose of the DHCPv6 Guard?
Community Votes
62% of anonymous learners picked answer D. Votes are pick records left by other test-takers — they are not the verified answer.
Community Insight
Tests the purpose and direction of DHCPv6 Guard filtering: it drops server-originated Advertise/Reply messages from rogue DHCPv6 servers or relays, not legitimate client-to-server traffic.
DHCPv6 Guard is an IPv6 First Hop Security feature that blocks DHCPv6 Advertise and Reply messages from unauthorized servers and relay agents, preventing rogue address assignment. This question tests that purpose, and option D is the intended correct answer.
Choosing A because the wording sounds like the guard relays messages between server and client; the trap is confusing a security filtering feature with a DHCPv6 message forwarding function.
Community Discussion (8 comments)
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Expert Analysis
Why the Answer Is Correct
DHCPv6 Guard is an IPv6 First Hop Security feature designed to prevent rogue DHCPv6 servers and unauthorized relay agents from handing out incorrect IPv6 addresses or other configuration. It does this by blocking DHCPv6 Advertise and Reply messages that originate from unauthorized DHCPv6 servers and relay agents that forward server messages to clients. Option D is the only choice that describes a blocking action against DHCPv6 messages, which matches the guard's filtering purpose. Although the option says "to a DHCPv6 server," the exam intent is the guard's role in stopping unauthorized server-side DHCPv6 messages. Therefore, D is the best answer among the four.Why the Other Options Are Wrong
Option A describes the guard as messaging or relaying between a server and a client, but DHCPv6 Guard is a security filter, not a message broker or relay. Option B is the opposite of the feature's purpose: allowing replies and advertisements from rogue servers is exactly what DHCPv6 Guard prevents. Option C says it shows clients of a DHCPv6 server are affected, which is irrelevant; the guard prevents rogue clients from being affected by unauthorized servers. None of these options capture the blocking behavior that defines DHCPv6 Guard.Community Comment Notes
krobo and Sammy3637 both summarize the feature as one that "blocks reply and advertisement messages" from unauthorized servers and relay agents, which aligns with D. Fenix7 adds that the guard "prevents rogue devices that are pretending to be legitimate DHCP servers," reinforcing the security objective. bk989 argues for A, but his own Cisco citation notes that client messages and relay-forward messages from clients to servers are not blocked, which actually highlights the direction issue in option D while supporting the overall blocking concept. dapardo said "Not sure but C makes more sense to me," and Pietjeplukgeluk noted "Seems they are all wrong," reflecting the poorly worded choices. The majority still selected D, and the feature description supports a blocking answer.Exam Strategy
Read the direction of the filter carefully: DHCPv6 Guard protects clients from rogue servers and relay agents, so it drops Advertise and Reply messages, not client-originated traffic. When options are imprecise, choose the one that describes blocking unauthorized DHCPv6 server messages.
Frequently Asked Questions
Does DHCPv6 Guard block client-to-server DHCPv6 messages?
No. The guard does not block client messages or relay-forward messages from clients to servers; it blocks Advertise and Reply messages from unauthorized servers and relays.
Why is option D correct when it says relay agents to a DHCPv6 server?
Option D is the intended blocking answer; DHCPv6 Guard blocks server-originated Advertise and Reply messages from unauthorized servers and relay agents, though the wording is imprecise.
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