Igmp support for vpns, Protocols and standards, Igmp configuration task list – H3C Technologies H3C S12500 Series Switches User Manual

Page 103

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

•