Which ICMPv6 type is Router Solicitation?

Which ICMPv6 type is Router Solicitation?

• A. 133 - Router Solicitation
• B. 128 - Echo Request
• C. 135 - Neighbor Solicitation
• D. 136 - Neighbor Advertisement

Answer: (A)

In ICMPv6, the Router Solicitation message is used by a host to actively ask on the local link for a Router Advertisement from routers. This helps the host quickly learn available routers and configure itself accordingly, which is part of IPv6 address autoconfiguration. The message type for Router Solicitation is 133, so it’s the correct choice. Why the other options don’t fit: Echo Request is the ping message used to test reachability, not to discover routers. Neighbor Solicitation and Neighbor Advertisement are part of the Neighbor Discovery Protocol for discovering and resolving link-layer addresses of neighbors, not for soliciting router advertisements.

In ICMPv6, the Router Solicitation message is used by a host to actively ask on the local link for a Router Advertisement from routers. This helps the host quickly learn available routers and configure itself accordingly, which is part of IPv6 address autoconfiguration. The message type for Router Solicitation is 133, so it’s the correct choice.

Why the other options don’t fit: Echo Request is the ping message used to test reachability, not to discover routers. Neighbor Solicitation and Neighbor Advertisement are part of the Neighbor Discovery Protocol for discovering and resolving link-layer addresses of neighbors, not for soliciting router advertisements.