84
Figure 34 IGMP proxying
The following types of interfaces are defined in IGMP proxying:
•
Host interface
—An interface that is in the direction toward the root of the multicast forwarding
tree. A host interface acts as a receiver host that is running IGMP. IGMP proxying must be
enabled on this interface. This interface is also called the "proxy interface."
•
Router
interface
—An interface that is in the direction toward the leaf of the multicast
forwarding tree. A router interface acts as a router that is running IGMP. IGMP must be
configured on this interface.
An IGMP proxy device maintains a group membership database, which stores the group
memberships on all the router interfaces. The host interfaces and router interfaces perform actions
based on this membership database.
•
The host interfaces respond to queries according to the membership database or send
join/leave messages when the database changes.
•
The router interfaces participate in the querier election, send queries, and maintain
memberships based on received IGMP reports.
IGMP support for VPNs
IGMP maintains group memberships on a per-interface basis. After receiving an IGMP message on
an interface, IGMP processes the packet within the VPN to which the interface belongs. IGMP only
communicates with other multicast protocols within the same VPN instance.
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
Query from Router A
Report from Router B
Ethernet
Router interface
Host interface
Proxy
Router B
Querier
Router A
Host B
Receiver
Host A
Receiver
Host C
Query from Router B
Report from Host
PIM domain
