Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
An IPv6 LAN is using SLAAC. Which message allows hosts to learn the default gateway and on-link prefix?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
Neighbor Solicitation
NS is used for address resolution and neighbor discovery functions, not for advertising the default gateway.
B
Best answer
Router Advertisement
Correct. RA messages provide prefix and default-router information.
C
Distractor review
DHCPv6 Solicit
SLAAC does not rely on DHCPv6 for default-gateway information.
D
Distractor review
ICMP Echo Reply
Echo messages do not advertise prefixes or gateways.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is selecting Neighbor Solicitation as the message that provides default gateway and prefix information. Neighbor Solicitation is part of the IPv6 Neighbor Discovery Protocol but is used only for address resolution and reachability confirmation, not for advertising routing information. Candidates might confuse the two because both are ICMPv6 messages involved in neighbor discovery. However, only Router Advertisement messages contain the network prefix and default gateway details necessary for SLAAC. Misunderstanding this distinction can lead to incorrect answers on the exam.
Technical deep dive
How to think about this question
IPv6 Stateless Address Autoconfiguration (SLAAC) enables hosts to configure their own IPv6 addresses without a DHCP server. This process relies heavily on ICMPv6 Router Advertisement (RA) messages, which routers send periodically or in response to Router Solicitation messages. RA messages contain critical network information such as the on-link prefix, default gateway address, and various flags that guide host configuration. This mechanism allows hosts to learn the network prefix and the default router's link-local address, enabling proper IPv6 routing and communication within the LAN. In the context of SLAAC, Router Advertisement messages are the authoritative source for prefix and default gateway information. Hosts listen for these RA messages to determine which prefixes are on-link and to identify the default router for outbound traffic. Neighbor Solicitation messages, by contrast, are used for address resolution and neighbor discovery but do not provide routing or prefix information. DHCPv6 can provide additional configuration details but is not required for default gateway discovery in SLAAC. ICMP Echo Reply messages serve diagnostic purposes and do not carry configuration data. A common exam trap is confusing Neighbor Solicitation with Router Advertisement messages because both are ICMPv6 types involved in neighbor discovery. However, only Router Advertisements carry prefix and default gateway information. In practical networks, relying on Router Advertisements ensures hosts can autonomously configure their IPv6 addresses and routing without manual intervention or DHCPv6 dependency, which is essential for scalable IPv6 deployments and aligns with Cisco’s implementation of IPv6 SLAAC in enterprise environments.
KKey Concepts to Remember
- Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.
- Hosts use Router Advertisement messages to learn the network prefix and the default router's link-local address for routing.
- Neighbor Solicitation messages are used for address resolution and neighbor discovery, not for advertising routing information.
- SLAAC does not require DHCPv6 to provide default gateway information, as this is supplied by Router Advertisements.
- ICMP Echo Reply messages are used for network diagnostics and do not carry prefix or default gateway data.
- IPv6 hosts listen for Router Advertisements to autonomously configure their IPv6 addresses and routing parameters.
- Router Advertisements include flags that instruct hosts on how to configure their addresses and whether to use DHCPv6.
- Confusing Neighbor Solicitation with Router Advertisement messages is a common exam trap related to IPv6 SLAAC.
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.
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More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.
What is the correct answer to this question?
The correct answer is: Router Advertisement — Hosts learn the default gateway and prefix information from Router Advertisement messages.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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