Leaving And Staying In Groups; Igmp Snooping - Dell PowerEdge M IO Aggregator Command Reference Manual

Leaving and Staying in Groups

Figure 9-5 shows how multicast routers track and refresh state changes in response to group-and-specific
and general queries.
1. Host 1 sends a message indicating it is leaving group 224.1.1.1 and that the included filter for 10.11.1.1
and 10.11.1.2 are no longer necessary.
2. The querier, before making any state changes, sends a group-and-source query to see if any other host
is interested in these two sources; queries for state-changes are retransmitted multiple times. If any are
interested, they respond with their current state information and the querier refreshes the relevant state
information.
3. Separately in
4. Host 2 responds to the periodic general query so the querier refreshes the state information for that
group.
Figure 9-5. IGMP Membership Queries: Leaving and Staying in Groups
Interface Multicast Group Filter Source Source
Address Timer Mode Timer
1/1 224.1.1.1 Include
10.11.1.1 LQMT
10.11.1.2 LQMT
224.2.2.2 GMI Exclude None
Type: 0x11
Group Address: 224.1.1.1
IGMP Group-and-Source
Number of Sources: 2
Specific Query
Source Address: 10.11.1.1, 10.11.1.2

IGMP Snooping

IGMP snooping is auto-configured on an Aggregator.
Multicast packets are addressed with multicast MAC addresses, which represent a group of devices rather
than one unique device. Switches forward multicast frames out of all ports in a VLAN by default, even if
there are only a small number of interested hosts, resulting in a waste of bandwidth. IGMP snooping
enables switches to use information in IGMP packets to generate a forwarding table that associates ports
with multicast groups so that received multicast frames are forwarded only to interested receivers.
Figure 9-5, the querier sends a general query to 224.0.0.1.
Membership Queries: Leaving and Staying
Querier
1/1
Queries retransmitted Last Member
Query Count times at Last Member
2
Query Interval
Type: 0x17
Number of Group Records: 1
Record Type: 6
1
Number of Sources: 2
Multicast Address: 224.1.1.1
Source Addresses: 10.11.1.1, 10.11.1.2
IGMP Leave message
Host 1
Non-Querier
Non-querier builds identical table
and waits Other Querier Present
Interval to assume Querier role
3
4
Host 2
Internet Group Management Protocol (IGMP) | 113
2/1
Type: 0x11
IGMP General
Group Address: 224.0.0.1
Membership Query
Number of Sources: 0
Type: 0x22
Number of Group Records: 1
Record Type: 2 IGMP Membership Report
Number of Sources: 0
Multicast Address: 224.2.2.2