Dell POWEREDGE M1000E - Manual (Page 1153)

Managing IPv4 and IPv6 Multicast 1153
What Is Multicast Tunneling?
If Multicast traffic is to be routed through a part of a network that does not
support multicasting (routers which are not multicast capable) then the
multicast packets are encapsulated in an IP datagram and sent as a unicast
packet. When the multicast router at the remote end of the tunnel receives
the packet, the router strips off the IP encapsulation and forwards the packet
as an IP Multicast packet. This process of encapsulating multicast packets in
IP is called tunneling.
What Is IGMP?
The Internet Group Management Protocol (IGMP) is used by IPv4 systems
(hosts, L3 switches, and routers) to report their IP multicast group
memberships to any neighboring multicast routers. The PowerConnect
M6220/M6348/M8024/M8024-k switch performs the multicast router role of
the IGMP protocol, which means it collects the membership information
needed by the active multicast routing protocol.
The PowerConnect M6220/M6348/M8024/M8024-k switch supports IGMP
Version 3. Version 3 adds support for source filtering, which is the ability for a
system to report interest in receiving packets only from specific source
addresses, as required to support Source-Specific Multicast [SSM], or from all
but specific source addresses, sent to a particular multicast address. Version 3
is designed to be interoperable with Versions 1 and 2.
Understaning IGMP Proxy
IGMP proxy enables a multicast router to learn multicast group membership
information and forward multicast packets based upon the group
membership information. The IGMP Proxy is capable of functioning only in
certain topologies that do not require Multicast Routing Protocols (i.e.,
DVMRP, PIM-DM, and PIM-SM) and have a tree-like topology, as there is no
support for features like reverse path forwarding (RPF) to correct packet route
loops.
The proxy contains many downstream interfaces and a unique upstream
interface explicitly configured. It performs the host side of the IGMP protocol
on its upstream interface and the router side of the IGMP protocol on its
downstream interfaces.