mediumMultiple Choice
300-410 Practice Question: Runs the following command to troubleshoot DHCPv6…
A network engineer runs the following command to troubleshoot DHCPv6 relay on router R1:
R1# debug ipv6 dhcp relay
Output: IPv6 DHCP relay: Received SOLICIT message from FE80::1 on GigabitEthernet0/0 IPv6 DHCP relay: Forwarding SOLICIT to server 2001:DB8:2::1 via GigabitEthernet0/1 IPv6 DHCP relay: Received ADVERTISE message from server 2001:DB8:2::1 via GigabitEthernet0/1 IPv6 DHCP relay: Forwarding ADVERTISE to client FE80::1 via GigabitEthernet0/0 IPv6 DHCP relay: Received REQUEST message from FE80::1 on GigabitEthernet0/0 IPv6 DHCP relay: Forwarding REQUEST to server 2001:DB8:2::1 via GigabitEthernet0/1 IPv6 DHCP relay: Received REPLY message from server 2001:DB8:2::1 via GigabitEthernet0/1 IPv6 DHCP relay: Forwarding REPLY to client FE80::1 via GigabitEthernet0/0
What does this output indicate?
⚠ Common exam trap
Cisco often tests the ability to interpret debug output by showing a successful message flow, leading candidates to incorrectly assume a failure because they expect an error message or because they misread the link-local address as a global address.
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 DHCPv6 relay agent is successfully forwarding messages between the client and server.
The debug output shows a complete DHCPv6 four-message exchange (SOLICIT-ADVERTISE-REQUEST-REPLY) being relayed between the client (FE80::1) and the server (2001:DB8:2::1). Each message is received on one interface and forwarded out the other, confirming the relay agent is functioning correctly. Therefore, option B is correct.
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 DHCPv6 relay agent is not functioning because messages are not being forwarded.
Why it's wrong here
The debug shows SOLICIT, ADVERTISE, REQUEST and REPLY each forwarded in both directions, so relay is working end to end. This option would fit if messages arrived but no forwarding lines appeared, indicating a relay configuration fault.
- ✓
The DHCPv6 relay agent is successfully forwarding messages between the client and server.
Why this is correct
The debug trace shows SOLICIT and ADVERTISE, then REQUEST and REPLY, each relayed in both directions between client FE80::1 and server 2001:DB8:2::1. Complete four-message exchange confirms the relay agent is forwarding correctly, satisfying the troubleshooting scenario.
- ✗
The DHCPv6 server is unreachable because no REPLY is received.
Why it's wrong here
The log shows a REPLY received from 2001:DB8:2::1 and forwarded to the client, so the server is demonstrably reachable and the four-message exchange completed. It is tempting because a missing REPLY is the classic signature of an unreachable DHCPv6 server, but that symptom would appear as repeated SOLICIT retransmissions with no ADVERTISE or REPLY.
- ✗
The DHCPv6 client is using a global unicast address as its link-local address.
Why it's wrong here
Every client message arrives from FE80::1, a link-local address, which is the expected source for DHCPv6 clients on the local segment. It is tempting because a client misconfigured with a global address as its link-local would look similar in a capture, but the FE80:: prefix here proves the address is genuinely link-local.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.