Quick Answer
The answer is the Router Advertisement message. In an IPv6 LAN using SLAAC, routers periodically send or respond to Router Solicitations with Router Advertisements that contain both the on-link prefix for address autoconfiguration and the default gateway information, allowing hosts to automatically configure their addresses and routing without manual intervention. On the CCNA 200-301 v2 exam, this concept tests your understanding of how SLAAC differs from stateful DHCPv6, and a common trap is confusing Neighbor Solicitation messages, which handle address resolution and DAD, with the RA’s role in gateway and prefix learning. Remember the mnemonic: “RA gives the GAteway and Prefix” — the Router Advertisement is the single message that provides both the default gateway and the on-link prefix in a SLAAC environment.
This 200-301 practice question tests your understanding of network infrastructure and connectivity. 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. A key principle to apply: router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.. 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.
An IPv6 LAN is using SLAAC. Which message allows hosts to learn the default gateway and on-link prefix?
Neighbor Solicitation
Why wrong: NS is used for address resolution and neighbor discovery functions, not for advertising the default gateway.
Router Advertisement
Correct. RA messages provide prefix and default-router information.
DHCPv6 Solicit
Why wrong: SLAAC does not rely on DHCPv6 for default-gateway information.
ICMP Echo Reply
Why wrong: Echo messages do not advertise prefixes or gateways.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Router Advertisement
In an IPv6 LAN using SLAAC (Stateless Address Autoconfiguration), hosts learn the default gateway and on-link prefix from Router Advertisement (RA) messages sent by routers. Neighbor Solicitation (NS) is used for address resolution and Duplicate Address Detection (DAD), not for learning gateway/prefix. DHCPv6 Solicit is part of stateful DHCPv6, not SLAAC. ICMP Echo Reply is a simple reachability test and provides no configuration information.
Key principle: Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Neighbor Solicitation
Why it's wrong here
NS is used for address resolution and neighbor discovery functions, not for advertising the default gateway.
When this WOULD be correct
In a question asking about the process of resolving the link-layer address of a specific IPv6 neighbor, such as 'What message is sent by a host to find the MAC address of another device on the same subnet?', the correct answer would be Neighbor Solicitation.
Router Advertisement
Why this is correct
Correct. RA messages provide prefix and default-router information.
Related concept
Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.
DHCPv6 Solicit
When this WOULD be correct
If the question were about obtaining IPv6 configuration information from a DHCPv6 server instead of SLAAC, then 'DHCPv6 Solicit' would be the correct answer. For example, a question could ask which message is sent by a client to request an IPv6 address and other settings from a DHCPv6 server.
ICMP Echo Reply
Why it's wrong here
Echo messages do not advertise prefixes or gateways.
When this WOULD be correct
If the question asked which message is used to verify the reachability of a host or to troubleshoot network connectivity issues, then ICMP Echo Reply would be the correct answer, as it is specifically designed for that purpose.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is correct
Correct. RA messages provide prefix and default-router information.
Why this is wrong here
Neighbor Solicitation (NS) messages are used for address resolution (determining the link-layer address of a neighbor) and duplicate address detection, not for advertising default gateway or prefix information.
★ When this WOULD be the correct answer
In a question asking about the process of resolving the link-layer address of a specific IPv6 neighbor, such as 'What message is sent by a host to find the MAC address of another device on the same subnet?', the correct answer would be Neighbor Solicitation.
Why candidates choose this
Students may confuse Neighbor Solicitation with Router Solicitation or think that any neighbor discovery message provides gateway information.
Why this is wrong here
DHCPv6 Solicit messages are used in stateful DHCPv6 to request configuration parameters like addresses and DNS servers, but SLAAC does not use DHCPv6 for default gateway or prefix information; those are provided by RA messages.
★ When this WOULD be the correct answer
If the question were about obtaining IPv6 configuration information from a DHCPv6 server instead of SLAAC, then 'DHCPv6 Solicit' would be the correct answer. For example, a question could ask which message is sent by a client to request an IPv6 address and other settings from a DHCPv6 server.
Why candidates choose this
Students may think DHCPv6 is always required for IPv6 configuration, or confuse the roles of SLAAC and DHCPv6 in providing gateway information.
Why this is wrong here
ICMP Echo Reply messages are used for ping responses and do not carry any routing or prefix information; they are not involved in neighbor discovery or address autoconfiguration.
★ When this WOULD be the correct answer
If the question asked which message is used to verify the reachability of a host or to troubleshoot network connectivity issues, then ICMP Echo Reply would be the correct answer, as it is specifically designed for that purpose.
Why candidates choose this
Students might associate ICMP with IPv6 neighbor discovery or think that echo messages can convey network configuration, but they are purely for reachability testing.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
Be careful not to confuse the roles of Router Solicitation and Router Advertisement messages. Remember, solicitations are requests, while advertisements provide information.
Detailed technical explanation
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.
Key takeaway
Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Review router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Network Infrastructure and Connectivity — This question tests Network Infrastructure and Connectivity — Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC..
The correct answer is: Router Advertisement — In an IPv6 LAN using SLAAC (Stateless Address Autoconfiguration), hosts learn the default gateway and on-link prefix from Router Advertisement (RA) messages sent by routers. Neighbor Solicitation (NS) is used for address resolution and Duplicate Address Detection (DAD), not for learning gateway/prefix. DHCPv6 Solicit is part of stateful DHCPv6, not SLAAC. ICMP Echo Reply is a simple reachability test and provides no configuration information.
Review router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC., then practise related 200-301 questions on the same topic to reinforce the concept.
Router Advertisement messages advertise the on-link prefix and default gateway information to IPv6 hosts using SLAAC.
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Last reviewed: May 17, 2026
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