H3C Technologies H3C S7500E Series Switches - Manual (Page 115)

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forwarding tree. An upstream interface acts as a host running IGMP; therefore, it is also
called host interface.
z Downstream interface: An interface that is running IGMP and not in the direction toward the
root of the multicast forwarding tree. A downstream interface acts as a router running IGMP;
therefore, it is also called router interface.
A device with IGMP proxying configured maintains a group membership database, which
storesthe group memberships on all the downstream interfaces. Each entry comprises the
multicast address, filter mode, and source list. Such an entry is a collection of members in the
same multicast group on each downstream interface.
A proxy device performs host functions on the upstream interface based on the database. It
responds to queries according to the information in the database or sends join/leave messages
when the database changes. On the other hand, the proxy device performs router functions on
the downstream interfaces by participating in the querier election, sending queries, and
maintaining memberships based on the reports.
Multi-Instance IGMP
While IGMP maintains group memberships on a per-interface base, IGMP in a VPN instance
handles protocol packets based on the VPN instance on the interface. Upon receiving an IGMP
packet, the router determines the instance to which the message belongs and handles the
message within the instance. If IGMP running in a VPN instance needs to exchange information
with another multicast protocol, the router informs the other multicast protocol only within the
VPN instance.
Protocols and Standards
The following documents describe different IGMP versions:
z RFC 1112: Host Extensions for IP Multicasting
z RFC 2236: Internet Group Management Protocol, Version 2
z RFC 3376: Internet Group Management Protocol, Version 3
z RFC 4605: Internet Group Management Protocol (IGMP)/Multicast Listener Discovery
(MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")
IGMP Configuration Task List
Complete these tasks to configure IGMP:
Task Remarks
Enabling IGMP Required
Configuring IGMP Versions Optional
Configuring Static Joining Optional
Configuring Basic Functions
of IGMP
Configuring a Multicast Group Filter Optional