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DVMRP resembles the Routing Information Protocol (RIP),
but is extended for multicast delivery. It relies upon RIP hop
counts to calculate 'shortest paths' back to the source of a
multicast message, but defines a 'route cost' to calculate
which branches of a multicast delivery tree should be
'pruned' – once the delivery tree is established.
When a sender initiates a multicast, DVMRP initially
assumes that all users on the network will want to receive
the multicast message. When an adjacent router receives
the message, it checks its unicast routing table to determine
the interface that gives the shortest path (lowest cost) back
to the source. If the multicast was received over the shortest
path, then the adjacent router enters the information into its
tables and forwards the message. If the message is not
received on the shortest path back to the source, the
message is dropped.
Route cost is a relative number that is used by DVMRP to
calculate which branches of a multicast delivery tree should
be 'pruned'. The 'cost' is relative to other costs assigned to
other DVMRP routes throughout the network.
The higher the route cost, the lower the probability that the
current route will be chosen to be an active branch of the
multicast delivery tree (not 'pruned') – if there is an
alternative route.
Parameter
Interface Name:[
Neighbor Time Out
Interval:[35
Route Metric:[1 ]
60 VH-2402-L3 Management Guide
Description
]
Allows the entry of the name of the IP
interface for which DVMRP is to be
configured. This must be a previously
defined IP interface.
This field allows an entry between 1 and
]
65,535 seconds and defines the time
period for DVMRP will hold Neighbor
Router reports before issuing poison
route messages. The default is 35
seconds.
This field allows an entry between 0 and
254 and defines the route cost for the IP
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