hardMultiple ChoiceObjective-mapped
300-410 Practice Question: A router is configured as a DHCPv6 client on an…
A router is configured as a DHCPv6 client on an interface using 'ipv6 address dhcp'. The router receives a valid IPv6 address from the server, but the address is not used for outgoing traffic. Which is the most likely explanation?
⚠ Common exam trap
Cisco often tests the subtlety that a DHCPv6 client can receive an address but not use it if a static address is present, leading candidates to incorrectly suspect DHCPv6 configuration issues or routing problems.
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 router has a static IPv6 address configured on the same interface, and the DHCP-assigned address is not preferred for source selection.
When a router has both a static IPv6 address and a DHCPv6-assigned address on the same interface, the static address is typically preferred as the source address for outgoing traffic because it is manually configured and considered more stable. The DHCPv6-assigned address, while valid, is not selected as the source unless explicitly preferred via source-interface selection rules or policy. This explains why the address is received but not used.
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 router has a static IPv6 address configured on the same interface, and the DHCP-assigned address is not preferred for source selection.
Why this is correct
Correct: If a static address is present, the router may use it as the source, especially if it is in the same subnet as the destination.
- ✗
The DHCPv6 server assigned a temporary address (IA_TA) instead of a non-temporary address (IA_NA).
Why it's wrong here
Incorrect: The 'ipv6 address dhcp' command requests IA_NA, not IA_TA.
- ✗
The router's 'ipv6 unicast-routing' is disabled.
Why it's wrong here
Incorrect: Unicast routing is needed for forwarding, but the address would still be used.
- ✗
The DHCP-assigned address is in a different subnet than the default gateway.
Why it's wrong here
Incorrect: The DHCP server typically assigns an address from the same subnet as the client.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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