Dell PowerEdge XL 5133-4 MXL 10/40GbE Switch IO Module FTOS Command Reference - Page 125

IGMP Version 3 Conceptually, IGMP version 3 behaves the same as version 2. However, there are differences: • Version 3 adds the ability to filter by multicast source, which helps the multicast routing protocols avoid forwarding traffic to subnets where there are no interested receivers. • To enable filtering, routers must keep track of more state information, that is, the list of sources that must be filtered. An additional query type, the group-and-source-specific query, keeps track of state changes, while the group-specific and general queries still refresh existing state. • Reporting is more efficient and robust. Hosts do not suppress query responses (non-suppression helps track state and enables the immediate-leave and IGMP snooping features), state-change reports are retransmitted to insure delivery, and a single membership report bundles multiple statements from a single host, rather than sending an individual packet for each statement. To accommodate these protocol enhancements, the IGMP version 3 packet structure is different from version 2. Queries (Figure 9-2) are still sent to the all-systems address 224.0.0.1, but reports (Figure 9-3) are sent to all the IGMP version 3-capable multicast routers address 244.0.0.22. Figure 9-2. IGMP version 3 Membership Query Packet Format Type (0x11) Max. Response Code Checksum Group Address Reserved S Querier Robustness Querier's Query Number of Value Interval Code Sources (2) Source Addresses Maximum Response Time derived from this value Bit flag that when set to 1 suppresses router query response timer updates Query Interval derived from this value Source addresses to be filtered Code: 0x11: Membership Query Number of times that a router or receiver transmits a query or report to insure that it is received Number of source addresses to be filtered Figure 9-3. IGMP version 3 Membership Report Packet Format Version IHL (4) TOS (0xc0) Total Length Flags Frag Offset TTL (1) Protocol (2) Header Checksum Src IP Addr Dest IP Addr (224.0.0.22) Options (Router Alert) Padding IGMP Packet fnC0070mp Type Reserved 0x12: IGMP version 1 Membership Report 0x16: IGMP version 2 Membership Report 0x17: IGMP Leave Group 0x22: IGMP version 3 Membership Report Checksum Reserved Number of Group Records Group Record 1 Group Record 2 Group Record N Value used by IGMP to calculate multicast reception state Record Type Auxiliary Data Length (0) Number of Sources Multicast Address Source Addresses Auxiliary Data Length of Auxiliary Data field Group address to which the group record pertains None defined in RFC 3376 Range: 1-6 Number of source addresses Code: 1: Current state is Include to be filtered 2: Current state is Exclude 3: State change to Include 4: State change to Exclude 5: Allow new sources and no state change 6: Block old sources and no state change Source addresses to be filtered fnC0071mp Internet Group Management Protocol (IGMP) | 111