188 Understanding IPv6, Second Edition

- Icmpv6: Version 2 Multicast Listener Report

MessageType: Version 2 Multicast Listener Report, 143(0x8f)

-MulticastListenerReport: Reserved: 0 (0x0) CheckSum: 4122 (0x101A) Reserved1: 0 (0x0)

NrofMcastAddrRecords: 1 (0x1) - McastAddressRecord:

RecordType: CHANGE_TO_EXCLUDE_MODE, 4(0x04) AuxDataLen: 0, in units of 4 bytes NumberofSources: 0 (0x0)

MulticastAddress: FF02:0:0:0:0:0:1:3

Summary of MLDv2

Table 7-3 lists IGMPv3 messages and their corresponding MLDv2 equivalents.

Table 7-3 IGMPv3 Messages and Their MLDv2 Equivalents

MLD and MLDv2 Support in Windows Server 2008 and Windows Vista

IPv6 in Windows Server 2008 and Windows Vista supports both MLD and MLDv2. IPv6 in Windows Server 2008 and Windows Vista uses MLDv2 by default but will use MLD if it receives an MLD message. You can configure IPv6 to use MLD with the netsh interface ipv6 set global mldversion=version2 command. Note that the “version2” is referring to IGMPv2, the equivalent of which in IPv6 is MLD. The mldversion setting is common to both IPv4 and IPv6. You can configure IPv6 to use MLDv2 with the netsh interface ipv6 set global mldversion=version3 command; however, it will use MLD if it receives an MLD message.

IPv6 in Windows Server 2008 and Windows Vista supports IPv6 multicast forwarding, which you can enable with the netsh interface ipv6 set global multicastforwarding=enable command. However, at the time of the publication of this book, there is no mechanism to update the IPv6 multicast forwarding table. Entries in the IPv6 multicast forwarding table allow the IPv6 protocol to determine how to forward incoming IPv6 multicast traffic. An IGMP routing protocol component for the Windows Server 2008 Routing and Remote Access service allows a computer running Windows Server 2008 to act as an IPv4-based multicast forwarding router. There is no corresponding routing protocol component for MLD that allows a Windows Server 2008–based computer to act as an IPv6-based multicast forwarding router.

References

The following references were cited in this chapter:

■RFC 2236 — “Internet Group Management Protocol, Version 2”

■RFC 2710 — “Multicast Listener Discovery (MLD) for IPv6”

■RFC 2711 — “IPv6 Router Alert Option”

■RFC 3376 — “Internet Group Management Protocol, Version 3”

■RFC 3810 — “Multicast Listener Discovery Version 2 (MLDv2) for IPv6”

You can obtain these RFCs from the \RFCs_and_Drafts folder on the companion CD-ROM or from http://www.ietf.org/rfc.html.

Testing for Understanding

To test your understanding of MLD and MLDv2, answer the following questions. See Appendix D, “Testing for Understanding Answers,” to check your answers.

1.Why is the IPv6 Router Alert option used in the Hop-by-Hop Options header for MLD and MLDv2 messages?

2.Which addresses are used as the source address in MLD and MLDv2 messages?

3.Which addresses are used as the IPv6 destination address in MLD and MLDv2 messages?

4.How do you distinguish a general query from a multicast-address-specific query in the Multicast Listener Query message?

5.How do you distinguish a multicast-address-specific query from a multicast-address- and-source specific query in the MLDv2 Multicast Listener Query message?

6.For which multicast addresses are Multicast Listener Report messages never sent?

7.In which MLD message is the value of the Maximum Response Delay field significant?

8.Describe the use of the Multicast Address field for each MLD and MLDv2 message.