Igmp Interface Settings - D-Link xStack DES-3800 Series User Manual

xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
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:
Figure 8- 52. IGMP State Transitions

IGMP Interface Settings

The Internet Group Multicasting Protocol (IGMP) can be configured on the Switch on a per-IP
interface basis. To view the IGMP Interface Table, open the IP Multicast Routing Protocol folder
under Layer 3 Features and click IGMP Interface Settings. Each IP interface configured on the
Switch is displayed in the below IGMP Interface Table dialog box. To configure IGMP for a
particular interface, click the corresponding hyperlink for that IP interface. This will open another
IGMP Interface Configuration window:
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