D-Link DGS-3620-28PC-SI Product Manual page 212

xStack® DGS-3620 Series Managed Switch Web UI Reference Guide
The IGMP Type codes are shown below:
Type
0x11
0x11
0x16
0x17
0x12
IGMP packets enable multicast routers to keep track of the membership of multicast groups, on their respective
subnetworks. The following outlines what is communicated between a multicast router and a multicast group
member using IGMP.
A host sends an IGMP "report" to join a group
A host will never send a report when it wants to leave a group (for version 1).
A host will send a "leave" report when it wants to leave a group (for version 2).
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 Switch 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.
Meaning
Membership Query (if Group Address is 0.0.0.0)
Specific Group Membership Query (if Group Address is Present)
Membership Report (version 2)
Leave a Group (version 2)
Membership Report (version 1)
Table 5-1 IGMP Type Codes
Figure 5-66 IGMP State Transitions
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