Internet Control Message Protocol for IPv6 (ICMPv6)

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Internet Control Message Protocol for IPv6 (ICMPv6)

Internet Control Message Protocol for IPv6 (ICMPv6) is a required IPv6 standard defined in RFC 2463, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification." With ICMPv6, hosts and routers that use IPv6 communication can report errors and send simple echo messages.

The ICMPv6 protocol also provides a framework for the following:

• Multicast Listener Discovery (MLD)

  MLD is a series of three ICMPv6 messages that replace version 2 of the Internet Group Management Protocol (IGMP) for IPv4 to manage subnet multicast membership. For more information, see Multicast Listener Discovery (MLD).

• Neighbor Discovery (ND)

  Neighbor Discovery is a series of five ICMPv6 messages that manage node-to-node communication on a link. Neighbor Discovery replaces Address Resolution Protocol (ARP), ICMPv4 Router Discovery, and the ICMPv4 Redirect message and provides additional functions. For more information, see Neighbor Discovery (ND).

ICMPv6 messages are usually sent automatically when an IPv6 packet cannot reach its destination.

ICMPv6 messages are encapsulated and sent as the payload of IPv6 packets, as shown in the following illustration.

Different types of ICMPv6 messages are identified in the ICMPv6 header. Because ICMPv6 messages are carried in IPv6 packets, they are unreliable.

ICMPv6 messages that are not related to MLD or ND are listed and described in the following table.

ICMPv6 message	Description
Destination Unreachable	An error message that informs the sending host that a packet cannot be delivered.
Packet Too Big	An error message that informs the sending host that the packet is too large to forward.
Time Exceeded	An error message that informs the sending host that the Hop Limit of an IPv6 packet has expired.
Parameter Problem	An error message that informs the sending host that an error was encountered in processing the IPv6 header or an IPv6 extension header.
Echo Request	An informational message that is used to determine whether an IPv6 node is available on the network.
Echo Reply	An informational message that is used to reply to the ICMPv6 Echo Request message.

You can use the ping command to send ICMPv6 Echo Request messages and record the receipt of ICMPv6 Echo Reply messages. With ping, you can detect network or host communication failures and troubleshoot common IPv6 connectivity problems. For more information, see Test IPv6 connectivity by using the ping command.

You can use the tracert command to send ICMPv6 Echo Request messages with incrementally increasing values in the Hop Limit field. Tracert will trace and display the path taken by IPv6 packets between a source and destination, allowing you to troubleshoot common IPv6 routing problems. For more information, see Trace an IPv6 path by using the tracert command.

Note

• IPv6 is a rapidly evolving standard. The RFCs referenced might have been made obsolete by newer RFCs.