The Distance Vector Multicast Routing Protocol (DVMRP) is one of the earliest multicast routing protocols, designed to deliver a single stream of data efficiently to many recipients at once across an IP network. Instead of sending a separate copy of a packet to every receiver, DVMRP builds source-rooted distribution trees so that traffic is replicated only where the network branches toward interested hosts. It borrows its distance-vector logic from the Routing Information Protocol (RIP) and was the routing engine behind the historic Multicast Backbone (MBONE) of the early 1990s.
How DVMRP works
DVMRP combines a distance-vector routing table with a forwarding technique called Reverse Path Forwarding (RPF). Routers exchange periodic distance-vector updates so each one learns the shortest path back toward every multicast source. When a multicast packet arrives, the router checks whether it came in on the interface that lies on the reverse path to the source. If it did, the packet is forwarded onward; if not, it is discarded. This RPF check is what prevents loops and duplicate delivery.
To trim unnecessary traffic, DVMRP uses a flood-and-prune model. A new source’s traffic is initially flooded across the tree; routers with no downstream members then send prune messages upstream to stop the flow on branches that have no receivers. Pruned branches are periodically refreshed, and graft messages let a branch rejoin the tree quickly when a new member appears. DVMRP works alongside the Internet Group Management Protocol (IGMP), which is how end hosts signal that they want to join or leave a given multicast group.
DVMRP in practice: real-world uses
- MBONE: The experimental multicast backbone that carried IETF meeting audio and video, software distribution, and live events used DVMRP as its primary routing protocol.
- Audio and video conferencing: Early real-time conferencing tools relied on DVMRP to reach many participants without generating a separate unicast stream for each one.
- Internet radio and streaming: Multicast-based broadcasters used DVMRP so a single audio stream could serve a large, distributed audience while conserving bandwidth.
Advantages and limitations
DVMRP’s strengths are its simplicity and its efficient use of bandwidth compared with unicast or broadcast delivery: packets are replicated only at branch points, and receivers get data along the shortest reverse path. Its distance-vector foundation also lets it adapt automatically as the network topology changes.
Those same roots create its weaknesses. DVMRP scales poorly on large internetworks because the flood-and-prune cycle and the need to maintain source-specific state consume router memory and bandwidth. It suffers RIP-style slow convergence, which can cause temporary loops or packet loss after a topology change, and it lacks native support for classless inter-domain routing (CIDR). For these reasons DVMRP has largely been superseded by more scalable protocols such as Protocol Independent Multicast (PIM) and Multicast OSPF (MOSPF).
DVMRP FAQ
What is the Distance Vector Multicast Routing Protocol used for?
DVMRP is used to route multicast traffic, delivering one data stream to many recipients efficiently by building source-rooted distribution trees and forwarding packets only along paths that lead to interested receivers.
How does DVMRP differ from PIM?
DVMRP carries its own RIP-based distance-vector routing information and uses a flood-and-prune model, which limits scalability. Protocol Independent Multicast (PIM) instead relies on whatever unicast routing table is already present and offers sparse-mode operation that scales far better across large or sparse networks, which is why PIM has largely replaced DVMRP.
Is DVMRP still used today?
DVMRP is now mostly of historical interest. It was essential to the early MBONE, but production multicast deployments have moved to PIM and related protocols that scale better and support CIDR.
Related Technology Terms
- Routing Information Protocol (RIP)
- Internet Group Management Protocol (IGMP)
- Multicast Open Shortest Path First (MOSPF)
- Reverse Path Forwarding (RPF)
- Protocol Independent Multicast (PIM)