Ericsson ECN330, User Manual

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Configuring the ECN330-switch
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Figure 216 DVMRP Concept
When this router receives the multicast message, it checks its unicast routing
table to locate the port that provides the shortest path back to the source. If that
path passes through the same port on which the multicast message was
received, then this router records path information for the concerned multicast
group in its routing table and forwards the multicast message on to adjacent
routers, except for the port through which the message arrived. This process
eliminates potential loops from the tree and ensures that the shortest path (in
terms of hop count) is always used.
6.21.3.1 Configuring Global DVMRP Settings
DVMRP is used to route multicast traffic to nodes which have requested a
specific multicast service through IGMP. This router uses Reverse Path
Forwarding (RPF) to build a shortest-path delivery tree that begins at the source
and spreads out to reach group members through the network. RPF uses three
different techniques to dynamically reconfigure the multicast spanning tree:
broadcasting, pruning, and grafting.
Command Usage
Broadcasting periodically floods the network with traffic from any active
multicast server. If IGMP snooping is disabled, multicast traffic is flooded to all
ports on the router. However, if IGMP snooping is enabled, then the first packet
for any source group pair is flooded to all DVMRP downstream neighbors. If a
source
branch
leaf
leaf