Dvmrp; Mbone; Igmp - 3Com CoreBuilder 2500 User Manual

5-2 C 5: R
HAPTER OUTING WITH

IGMP

DVMRP

MBONE

IP M
ULTICAST
The CoreBuilder 2500 system is capable of dynamic multicast filtering
based on the Internet Group Management Protocol (IGMP). This protocol
ensures that multicast packets are flooded only to appropriate ports in a
routing interface.
IGMP tracks end station group membership within a multicast group.
Membership in a group is dynamic, and hosts can be a member of more
than one group at a time. The system avoids propagating multicast
broadcasts to the entire subnetwork by confining them within the
multicast group (a process called IGMP snooping).
The Distance Vector Multicast Routing Protocol (DVMRP) establishes
multicast delivery paths over a series of routing devices. DVMRP is a
distance-vector-routing protocol, similar to the IP Routing Information
Protocol (RIP). Multicast routers exchange distance vector updates that
contain lists of destinations and the distance in router hops to each
destination. They maintain this information in a routing table.
The Internet Multicast Backbone (MBONE) uses DVMRP. Because of
DVMRP, the CoreBuilder 2500 system can establish delivery paths without
direct connections to multicast routers.
The MBONE is the Internet's experimental multicast backbone network.
Users can test multicast applications and technology on the MBONE
without waiting for Internet multicast standards to be set. You can
connect to the MBONE through any Internet service provider (ISP).
MBONE routers forward multicast packets over an interface or over a
multicast tunnel only if the Time-To-Live (TTL) value in the packet is larger
than the tunnel's threshold. See "Multicast Tunnels" on page 5-5 for
more information about tunnels.
At software revisions earlier than 8.0, CoreBuilder 2500 systems that are
connected to the MBONE network support up to 16 IP multicast tunnels
or routing interfaces. CoreBuilder 2500 systems at revision 8.0 or later
support up to 32 IP multicast tunnels or routing interfaces connected to
the MBONE.