Pim-Dm - Dell PowerConnect M6220 Configuration Manual

console#configure
router ospf
router-id 3.3.1.1
exit
ip routing
ip multicast
ip igmp
ip pimsm
ip pimsm rp-address 1.1.1.1 224.0.0.0 240.0.0.0
interface vlan 15
routing
ip address 3.3.3.1 255.255.255.0
ip pimsm
ip igmp
ip ospf area 0
exit
interface vlan 30
routing
ip address 1.1.1.1 255.255.255.0
ip pimsm
ip igmp
ip ospf area 0
exit
exit

PIM-DM

PIM-DM protocol is a simple, protocol-independent multicast routing protocol. It uses existing unicast
routing table and join/prune/graft mechanism to build a tree. PIM-DM creates source-based shortest-
path distribution trees making use of Reverse Path Forwarding (RPF).
PIM-DM cannot be used to build a shared distribution tree, as PIM-SM can. PIM-DM assumes that
when a sender starts sending data, all downstream routers and hosts want to receive a multicast
datagram. PIM-DM initially floods multicast traffic throughout the network. Routers that do not have
any downstream neighbors send back Prune messages that instruct the upstream router to remove that
multicast route from its forwarding table. In addition to the Prune messages, PIM-DM makes use of two
more messages: Graft and Assert. Graft messages are used whenever a new host wants to join the group.
Assert messages are used to shut off duplicate flows onto the same multi-access network.
To minimize the repeated flooding of datagrams and subsequent pruning associated with a particular
source-group (S,G) pair, PIM-DM uses a State Refresh message. This message is sent by the router(s)
directly connected to the source and is propagated throughout the network. When received by a router
on its RPF interface, the State Refresh message causes an existing prune state to be refreshed. State
Refresh messages are generated periodically by the router directly attached to the source.
PIM-DM is appropriate for:
1. OSPF configuration is added as a unicast protocol for illustration purposes; static unicast routing could also be
configured.
124
Multicast
[NOTE: This router should be an RP.]