IPv6 no longer uses ARP broadcasts or IGMP. As a result, ICMPv6 provides additional services to communicate issues on the network, which include the following:

• Neighbor solicitation/advertisement: These types are used for the Neighbor Discovery Protocol (NDP) to provide a method for hosts to share their existence on the network.
• Multicast listener query/report: This is used to exchange group multicast information to routers and hosts.

To see an example of the many ICMPv6 messages communicating to other devices on the network, go to CloudShark (https://www.cloudshark.org/captures/fe65ed807bc3) and then download and open the file in Wireshark. Create a flow graph by completing the following steps:

• In the display filter, enter icmpv6 and press Enter to run the filter.
• Go to Statistics, and then Flow Graph.
• Once open, go to the lower left-hand corner and select the Limit to Display filter.

The results are as shown in the following screenshot, where I have zoomed in to show the transactions:

Some of the ICMPv6 reports have additional details. For example, in the following screenshot, we can see the details provided in a single report:

As you can see, ICMPv6 is a powerful protocol. In addition to error and information messages, ICMPv6 provides additional information on IPv6 router and host configuration.

As discussed, ICMP headers hold a value for Type and Code. Let's take a look at these two fields in order to help us understand what ICMP is trying to tell us.