Igmp Version 3 - D-Link xStack DGS-3324SRi User Manual

xStack DGS/DXS-3300 Series Layer 3 Stackable Gigabit Ethernet Switch User Manual
Multicast routers send IGMP queries (to the all-hosts group address: 224.0.0.1) periodically to see whether any group
members exist on their subnetworks. If there is no response from a particular group, the router assumes that there are no
group members on the network.
The Time-to-Live (TTL) field of query messages is set to 1 so that the queries will not be forwarded to other subnetworks.
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:

IGMP Version 3

The current release of the xStack DGS/DXS-3300 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
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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
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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
0x11
0x12
0x16
0x17
0x22
Figure 6- 162. IGMP State Transitions
Meaning
Membership Query
Version 1 Membership Report
Version 2 Membership Report
Version 2 Leave Group
IGMPv3 Membership Report
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