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xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
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IGMP version 2 introduces some enhancements such as a method to elect a multicast querier for each LAN, an explicit leave
message, and query messages that are specific to a given group.
The states a computer will go through to join or to leave a multicast group are shown below:
Figure 8- 63. IGMP State Transitions
IGMP Version 3
The current release of the xStack DES-3800 switch series now implements IGMPv3. Improvements of IGMPv3 over version 2
include:
• The introduction of the SSM or Source Specific Multicast. In previous versions of IGMP, the host would receive all packets
sent to the multicast group. Now, a host will receive packets only from a specific source or sources. This is done through the
implementation of include and exclude filters used to accept or deny traffic from these specific sources.
• In IGMP v2, Membership reports could contain only one multicast group whereas in v3, these reports can contain multiple
multicast groups and multiple sources within the multicast group.
• Leaving a multicast group could only be accomplished using a specific leave message in v2. In v3, leaving a multicast
group is done through a Membership report which includes a block message in the group report packet.
• For version 2, the host could respond to a group query but in version 3, the host is now capable to answer queries specific to
the group and the source.
IGMP v3 is backwards compatible with other versions of IGMP.
The IGMPv3 Type supported codes are shown below:
Type Meaning
0x11 Membership Query
0x12 Version 1 Membership Report
0x16 Version 2 Membership Report
0x17 Version 2 Leave Group
0x22 IGMPv3 Membership Report