Intel 480T, User Manual

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C H A P T E R 1 2 IP Multicast Routing
IP multicast routing consists of the following functions:
• A router that can forward IP multicast packets.
• A router-to-router multicast routing protocol (for example, Distance
Vector Multicast Routing Protocol (DVMRP) or Protocol
Independent Multicast (PIM)).
• A method for the IP host to communicate its multicast group
membership to a router (for example, Internet Group Management
Protocol (IGMP)).
Note You should configure IP unicast routing before you
configure IP multicast routing.
DVMRP Overview
DVMRP is a distance vector protocol that is used to exchange routing
and multicast information between routers. Like RIP, DVMRP
periodically sends the entire routing table to its neighbors.
DVMRP has a mechanism that allows it to prune and graft multicast
trees to reduce the bandwidth consumed by IP multicast traffic.
PIM-DM Overview
Protocol Independent Multicast-Dense Mode (PIM-DM) is a
multicast routing protocol that is similar to DVMRP.
PIM-DM routers perform reverse path multicasting (RPM).
However, instead of exchanging its own unicast route tables for the
RPM algorithm, PIM-DM uses the existing unicast route table for the
reverse path. As a result, PIM-DM requires less system memory.
Using PIM-DM, multicast routes are pruned and grafted in the same
way as DVMRP.
Note You can run either DVMRP or PIM-DM on the switch, but
not both simultaneously.