Exam 300-101 Question id=421 Layer 3 Technologies

A packet capture log indicates that several router solicitation messages were sent from a local host on the Ipv6 segment. What is the expected acknowledgment and its usage?

A. Router acknowledgment messages will be forwarded upstream, where the DHCP server will allocate addresses to the local host.
B. Routers on the Ipv6 segment will respond with an advertisement that provides an external path from the local subnet, as well as certain data, such as prefix discovery.
C. Duplicate Address Detection will determine if any other local host is using the same Ipv6 address for communication with the Ipv6 routers on the segment.
D. All local host traffic will be redirected to the router with the lowest ICMPv6 signature, which is statically defined by the network administrator.

Router Advertisements (RA) are sent in response to router solicitation messages. Router solicitation messages, which have a value of 133 in the Type field of the ICMP packet header, are sent by hosts at system startup so that the host can immediately autoconfigure without needing to wait for the next scheduled RA message. Given that router solicitation messages are usually sent by hosts at system startup (the host does not have a configured unicast address), the source address in router solicitation messages is usually the unspecified Ipv6 address (0:0:0:0:0:0:0:0). If the host has a configured unicast address, the unicast address of the interface sending the router solicitation message is used as the source address in the message. The destination address in router solicitation messages is the all-routers multicast address with a scope of the link. When an RA is sent in response to a router solicitation, the destination address in the RA message is the unicast address of the source of the router solicitation message.
RA messages typically include the following information:

  • One or more onlink Ipv6 prefixes that nodes on the local link can use to automatically configure their Ipv6 addresses
  • Lifetime information for each prefix included in the advertisement
  • Sets of flags that indicate the type of autoconfiguration (stateless or stateful) that can be completed
  • Default router information (whether the router sending the advertisement should be used as a default router and, if so, the amount of time (in seconds) the router should be used as a default router)
  • Additional information for hosts, such as the hop limit and MTU a host should use in packets that it originates


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