D-Link DES-3326 User Manual page 195

DES-3326 Layer 3 Fast Ethernet Switch User's Guide
networks, and can be considered as a 'best-effort' multicasting
protocol. See Chapter 5, Distance-Vector Multicasting
Routing Protocol for more information.
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.
message is not received on the shortest path back to the source, the
message is dropped.
The NMR Report Timer:[35
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.
The Route Cost:[1 ] field allows an entry between 1 and 255 and
defines the route cost for the IP interface. The DVMRP route cost
is a relative number that represents the real cost of using this
route in the construction of a multicast delivery tree. It is similar
to, but not defined as, the hop count in RIP. The default cost is 1.
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.
Note: The higher the route cost, the lower the probability
that the current route will be chosen to be an active branch
Configuring the Switch Using the Console Interface
If the
] This field allows an entry
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