Question 1,033 of 2,152

DHCP (IPv4 and IPv6) →hardMultiple ChoiceObjective-mapped

DHCPv6 Relay Agent: Relay Destination on Wrong Interface

This 300-410 practice question tests your understanding of dhcp (ipv4 and ipv6). This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 router configured as a DHCPv6 relay agent is not forwarding DHCPv6 requests from clients to the server. The relay interface has 'ipv6 dhcp relay destination' configured. Clients are on a different VLAN. Which is the most likely explanation?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

A
The relay destination is configured on the client-facing interface; it should be on the server-facing interface.
Correct: The 'ipv6 dhcp relay destination' command must be applied to the interface that receives client requests (client-facing), not the server-facing interface.
B
The DHCPv6 server is not reachable via the relay agent's routing table.
Why wrong: Incorrect: While this could be an issue, the more common misconfiguration is the interface placement.
C
The relay agent must have 'ipv6 dhcp server' configured to act as a server.
Why wrong: Incorrect: Relay and server functions are separate; a relay does not need server configuration.
D
The clients are using DHCPv4, not DHCPv6.
Why wrong: Incorrect: The configuration is for DHCPv6, but the question states DHCPv6.

Full breakdown with real-world context →

Quick Answer

The answer is that the relay destination is configured on the client-facing interface when it should be on the server-facing interface. This is because a DHCPv6 relay agent must forward client requests toward the server, meaning the `ipv6 dhcp relay destination` command must be applied on the interface that has a route to the DHCP server, not on the interface where clients are sending their solicit messages. On the Cisco CCNP ENARSI 300-410 exam, this scenario tests your understanding of DHCPv6 relay placement and the distinction between client-facing and server-facing roles; a common trap is assuming the relay command belongs on the same VLAN as the clients. The core concept is that the relay agent listens for client messages on one interface and then unicasts them out a different interface toward the server. A useful memory tip is "relay toward the server, listen from the client"—the destination address always points away from the client subnet.

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 relay destination is configured on the client-facing interface; it should be on the server-facing interface.

The 'ipv6 dhcp relay destination' command must be configured on the interface facing the DHCPv6 clients, not the server-facing interface. This command instructs the router to intercept DHCPv6 messages arriving on that interface and forward them as relay-forward messages to the specified DHCPv6 server. Placing it on the server-facing interface would cause the router to attempt relaying on the wrong interface, so client requests on the client-facing VLAN are never intercepted or forwarded.

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 relay destination is configured on the client-facing interface; it should be on the server-facing interface.
Why this is correct
Correct: The 'ipv6 dhcp relay destination' command must be applied to the interface that receives client requests (client-facing), not the server-facing interface.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The DHCPv6 server is not reachable via the relay agent's routing table.
Why it's wrong here
Incorrect: While this could be an issue, the more common misconfiguration is the interface placement.
✗
The relay agent must have 'ipv6 dhcp server' configured to act as a server.
Why it's wrong here
Incorrect: Relay and server functions are separate; a relay does not need server configuration.
✗
The clients are using DHCPv4, not DHCPv6.
Why it's wrong here
Incorrect: The configuration is for DHCPv6, but the question states DHCPv6.

Common exam traps

Common exam trap: answer the scenario, not the keyword

Cisco often tests the misconception that the relay destination should be placed on the interface facing the DHCP server, when in fact it must be on the interface facing the DHCP clients to intercept their messages.

Detailed technical explanation

How to think about this question

DHCPv6 relay agents operate per RFC 3315, where the relay agent listens for Solicit and Request messages on the client-facing interface and encapsulates them in Relay-forward messages sent to the server. The 'ipv6 dhcp relay destination' command must be applied on the interface where client messages are received; the relay agent then uses its routing table to forward the encapsulated message to the server address. A common real-world scenario is when clients reside in a different VLAN (e.g., VLAN 10) and the relay agent's interface in that VLAN must have the destination configured, not the interface connecting to the server's VLAN.

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.

Visual reference

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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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 relay destination is configured on the client-facing interface; it should be on the server-facing interface. — The 'ipv6 dhcp relay destination' command must be configured on the interface facing the DHCPv6 clients, not the server-facing interface. This command instructs the router to intercept DHCPv6 messages arriving on that interface and forward them as relay-forward messages to the specified DHCPv6 server. Placing it on the server-facing interface would cause the router to attempt relaying on the wrong interface, so client requests on the client-facing VLAN are never intercepted or forwarded.

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.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

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