- A
The client includes the Rapid Commit option in the Solicit message to request rapid commit.
Correct. The client sets the Rapid Commit option in the Solicit message to indicate that it wants a two-message exchange.
- B
The server must be configured with the 'ipv6 dhcp server rapid-commit' command to honor rapid commit requests.
Correct. This command enables the server to respond with a Reply message immediately upon receiving a Solicit with the Rapid Commit option.
- C
If the server does not support rapid commit, it sends a Reply message with an error code.
Why wrong: Incorrect. If the server does not support rapid commit, it simply ignores the Rapid Commit option and proceeds with the normal four-message exchange (sending an Advertise).
- D
Rapid commit reduces the DHCPv6 exchange from six messages to four.
Why wrong: Incorrect. Rapid commit reduces the exchange from four messages (Solicit, Advertise, Request, Reply) to two (Solicit, Reply).
- E
Rapid commit is enabled by default on Cisco IOS DHCPv6 servers.
Why wrong: Incorrect. Rapid commit is not enabled by default; it must be explicitly configured with the 'ipv6 dhcp server rapid-commit' command.
DHCPv6 Rapid Commit Two-Message Exchange
This 300-410 practice question tests your understanding of dhcp (ipv4 and ipv6). 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 DHCPv6 rapid commit are true? (Choose TWO.)
Quick Answer
The correct answer is that the server must be configured with the `ipv6 dhcp server rapid-commit` command to honor rapid commit requests. This is true because DHCPv6 rapid commit, defined in RFC 3315, enables a streamlined two-message exchange—Solicit and Reply—instead of the standard four-message process. The client signals support by including a Rapid Commit option in its Solicit message, but the server must explicitly enable this feature; otherwise, it ignores the option and the client falls back to the normal exchange. On the Cisco CCNP ENARSI 300-410 exam, this topic tests your understanding of DHCPv6 optimization and configuration nuances—a common trap is assuming the client needs a separate command, but it does not. Remember the memory tip: “Client asks, server commits—only the server needs the `rapid-commit` fit.”
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
The client includes the Rapid Commit option in the Solicit message to request rapid commit.
Option A is correct because RFC 3315 defines the Rapid Commit option (Option 14) that a DHCPv6 client includes in its Solicit message to request a two-message exchange (Solicit/Reply) instead of the normal four-message exchange (Solicit/Advertise/Request/Reply). This reduces latency and is useful in environments where quick address assignment is critical.
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.
- ✓
The client includes the Rapid Commit option in the Solicit message to request rapid commit.
Why this is correct
Correct. The client sets the Rapid Commit option in the Solicit message to indicate that it wants a two-message exchange.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
The server must be configured with the 'ipv6 dhcp server rapid-commit' command to honor rapid commit requests.
Why this is correct
Correct. This command enables the server to respond with a Reply message immediately upon receiving a Solicit with the Rapid Commit option.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
If the server does not support rapid commit, it sends a Reply message with an error code.
Why it's wrong here
Incorrect. If the server does not support rapid commit, it simply ignores the Rapid Commit option and proceeds with the normal four-message exchange (sending an Advertise).
- ✗
Rapid commit reduces the DHCPv6 exchange from six messages to four.
Why it's wrong here
Incorrect. Rapid commit reduces the exchange from four messages (Solicit, Advertise, Request, Reply) to two (Solicit, Reply).
- ✗
Rapid commit is enabled by default on Cisco IOS DHCPv6 servers.
Why it's wrong here
Incorrect. Rapid commit is not enabled by default; it must be explicitly configured with the 'ipv6 dhcp server rapid-commit' command.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that rapid commit reduces the message count from six to four (confusing it with DHCPv4's four-message exchange) or that it is enabled by default, when in fact it must be explicitly configured and reduces the exchange to two messages.
Trap categories for this question
Command / output trap
Incorrect. Rapid commit is not enabled by default; it must be explicitly configured with the 'ipv6 dhcp server rapid-commit' command.
Detailed technical explanation
How to think about this question
Under the hood, the Rapid Commit option (Option 14) in the Solicit message signals the server to skip the Advertise and Request steps, directly sending a Reply with assigned addresses and configuration. This is particularly useful in mobile or IoT scenarios where clients need fast network attachment, but it requires careful server configuration to avoid conflicts in shared network segments.
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 practitioner preparing for the 300-410 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Questions learners often ask
What does this 300-410 question test?
DHCP (IPv4 and IPv6) — This question tests DHCP (IPv4 and IPv6) — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The client includes the Rapid Commit option in the Solicit message to request rapid commit. — Option A is correct because RFC 3315 defines the Rapid Commit option (Option 14) that a DHCPv6 client includes in its Solicit message to request a two-message exchange (Solicit/Reply) instead of the normal four-message exchange (Solicit/Advertise/Request/Reply). This reduces latency and is useful in environments where quick address assignment is critical.
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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