Processing Of Multicast Protocol Messages - H3C S7500E Series Operation Manual

Operation Manual – Multicast
H3C S7500E Series Ethernet Switches
forwards it through all its router ports in the VLAN and all member ports for that
multicast group, and performs the following:
If any IGMP report in response to the group-specific query is heard on a member
port before its aging timer expires, this means that some host attached to the port
is receiving or expecting to receive multicast data for that multicast group. The
switch resets the aging timer of the member port.
If no IGMP report in response to the group-specific query is heard on a member
port before its aging timer expires, this means that no hosts attached to the port
are still listening to that group address: the switch removes the port from the
outgoing port list of the forwarding table entry for that multicast group when the
aging timer expires.

2.1.4 Processing of Multicast Protocol Messages

With Layer 3 multicast routing enabled, an IGMP Snooping switch processes multicast
protocol messages differently under different conditions, specifically as follows:
1) If only IGMP is enabled, or both IGMP and PIM are enabled on the switch, the
switch handles multicast protocol messages in the normal way.
2) In only PIM is enabled on the switch:
The switch broadcasts IGMP messages as unknown messages in the VLAN.
Upon receiving a PIM hello message, the switch will maintain the corresponding
router port.
3) When IGMP is disabled on the switch, or when IGMP forwarding entries are
cleared (by using the reset igmp group command):
If PIM is disabled, the switch clears all its Layer 2 multicast entries and router
ports.
If PIM is enabled, the switch clears only its Layer 2 multicast entries without
deleting its router ports.
4) When PIM is disabled on the switch:
If IGMP is disabled, the switch clears all its router ports.
If IGMP is enabled, the switch maintains all its Layer 2 multicast entries and router
ports.
2.1.5 Protocols and Standards
IGMP Snooping is documented in:
RFC 4541: Considerations for Internet Group Management Protocol (IGMP) and
Multicast Listener Discovery (MLD) Snooping Switches
Chapter 2 IGMP Snooping Configuration
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