SMC Networks SMC8612XL3 F 1.0.1.3 Management Manual page 381

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 packet is received
through an interface that the router determines to be the shortest path
back to the source (based on interface metrics), then the router forwards
the packet on all interfaces except for the incoming interface.
The router will transmit a prune message back out the receiving interface
(i.e., the parent interface) to its upstream neighboring router if there are no
group members on its child interfaces. A prune message tells the upstream
router to stop forwarding packets for a particular source-group pair for the
prune lifetime.
If the router that previously sent a prune message now discovers a new
group member on one of its connections, it sends a graft message to the
upstream router. When an upstream router receives this message, it cancels
the prune message. If necessary, graft messages are propagated back
toward the source until reaching the nearest live branch in the multicast
tree.
The global settings that control the prune and graft messages (i.e., prune
lifetime) should be configured to the same values on all routers throughout
the network to allow DVMRP to function properly. However, if you
encounter problems in maintaining a multicast flow, then you may need to
modify the protocol variables which control the exchange of topology
information between DVMRP routers; such as the probe interval,
neighbor timeout or report interval.
Command Attributes
• DVMRP Protocol – Enables/disables DVMRP globally. (Default:
Disabled)
• Probe Interval – Sets the interval for sending neighbor probe
messages to the multicast group address for all DVMRP routers. Probe
messages are sent to neighboring DVMRP routers from which this
device has received probes, and is used to verify whether or not these
M R
ULTICAST OUTING
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