H3C Technologies H3C S12500 Series Switches - Manual (Page 103)

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An upstream interface acts as a host that is running IGMP. Therefore, it is also called the "host
interface."
• Downstream interface—An interface that is running IGMP and is not in the direction toward the
root of the multicast forwarding tree. A downstream interface acts as a router that is running IGMP.
Therefore, it is also called the "router interface."
An IGMP proxy device maintains a group membership database, which stores the 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.
An IGMP 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 IGMP proxy device performs router functions on the
downstream interfaces by participating in the querier election, sending queries, and maintaining
memberships based on the reports.
IGMP support for VPNs
IGMP maintains group memberships on a per-interface base. After receiving an IGMP message on an
interface, IGMP processes the packet within the VPN to which the interface belongs. If IGMP that runs in
a VPN needs to exchange information with another multicast protocol, it passes the information only to
the protocol that runs in this VPN.
Protocols and standards
• RFC 1112, Host Extensions for IP Multicasting
• RFC 2236, Internet Group Management Protocol, Version 2
• RFC 3376, Internet Group Management Protocol, Version 3
• RFC 4605, Internet Group Management Protocol (IGMP)/Multicast Listener Discovery (MLD)-Based
Multicast Forwarding ("IGMP/MLD Proxying")
IGMP configuration task list
Task Remarks
Configuring basic IGMP
functions
Enabling IGMP Required.
Configuring IGMP versions Optional.
Configuring static joining Optional.
Configuring a multicast group filter Optional.
Setting the maximum number of multicast groups that an
interface can join
Optional.
Adjusting IGMP performance
Configuring Router-Alert option handling methods Optional.
Configuring IGMP query and response parameters Optional.
Configuring IGMP fast-leave processing Optional.
Enabling the IGMP host tracking function Optional.