System information

Configuring IP Multicast Routing
8-9
About DVMRP
The Distance Vector Multicast Routing Protocol (DVMRP) is a distance-vector
multicast routing protocol that delivers connectionless data to a group of hosts across
an internetwork. DVMRP is designed to be used as an interior gateway protocol (IGP)
within a multicast domain.
DVMRP is often referred to as a "flood and prune" protocol. DVMRP dynamically
creates IP multicast delivery trees by using Reverse Path Forwarding (RPF) to
forward multicast traffic away from the source to downstream interfaces. RPF uses
the DVMRP routing table to determine the upstream and downstream neighbors. The
source sends traffic to an arbitrary group of hosts that are represented by a multicast
group address. The multicast router must determine which direction is upstream
(towards the source) and which direction (or directions) is downstream. If there are
multiple downstream paths, the router replicates the packet and forwards it to the
appropriate downstream paths (which may not be all paths). The router forwards a
multicast packet once it is received on the upstream interface.
These methods allow the formation of shortest-path trees, which are used to reach all
group members from each network source of multicast traffic.
DVMRP routers dynamically discover their neighbors by sending neighbor probe
messages periodically to an IP multicast group address that is reserved for all
DVMRP routers.
Configuring DVMRP Routing Information
Use the following sections to configure DVMRP routing information on the BSR:
• Enabling DVMRP on the Router
• Configuring the DVMRP Route Expiration Threshold
• Configuring the DVMRP Route Reporting Threshold
• Limiting the Number of DVMRP Routes
• Setting the DVMRP Prune Lifetime Value
Enabling DVMRP on the Router
Follow these steps to configure general DVMRP parameters: