DVMRP Settings
To configure DVMRP for an IP interface:
Click the DVMRP Settings link on the IP Multicasting menu:
Figure 7-44. DVMRP Interface Configuration window
This menu allows the
The Distance Vector Multicast Routing Protocol (DVMRP) is a
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.
