Dvmrp Interface Configuration - D-Link xStack DES-3800 Series User Manual

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DVMRP Interface Configuration

The Distance Vector Multicast Routing Protocol (DVMRP) is a hop-based method of building
multicast delivery trees from multicast sources to all nodes of a network. Because the delivery trees
are 'pruned' and 'shortest path', DVMRP is relatively efficient. Because multicast group membership
information is forwarded by a distance-vector algorithm, propagation is slow. DVMRP is optimized
for high delay (high latency) relatively low bandwidth networks, and can be considered as a 'best-
effort' multicasting protocol.
DVMRP resembles the Routing Information Protocol (RIP), but is extended for multicast delivery.
DVMRP builds a routing table to calculate 'shortest paths' back to the source of a multicast message,
but defines a 'route cost' (similar to the hop count in RIP) as a relative number that represents the real
cost of using this route in the construction of a multicast delivery tree to be 'pruned' - once the
delivery tree has been 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.
DVMRP Global Settings
To enable DVMRP globally on the Switch, click Layer 3 Features > IP Multicast Routing Protocol
> DVMRP Global Settings. This will give the user access to the following screen:
xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
Sets the maximum amount of time allowed before sending an IGMP response report.
A value between 1 and 25 seconds can be entered, with a default of 10 seconds.
A tuning variable to allow for subnetworks that are expected to lose a large number of
packets. A value between 1 and 255 can be entered, with larger values being
specified for subnetworks that are expected to lose larger numbers of packets.
Specifies the maximum amount of time between group-specific query messages,
including those sent in response to leave group messages. A value between 1 and 25.
The default is 1 second.
This field can be toggled between Enabled and Disabled and enables or disables
IGMP for the IP interface. The default is Disabled.
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