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Configuring DVMRP Interoperability
Advanced DVMRP Interoperability Configuration Task List
IPC-540
Cisco IOS IP Configuration Guide
See the “DVMRP Tunnel Example” section later in this chapter for an example of how to configure a
DVMRP tunnel.
Advertising Network 0.0.0.0 to DVMRP Neighbors
The mrouted protocol is a public domain implementation of DVMRP. If your router is a neighbor to an
mrouted Version 3.6 device, you can configure the Cisco IOS software to advertise network 0.0.0.0 to
the DVMRP neighbor. Do not advertise the DVMRP default into the MBONE. You must specify whether
only route 0.0.0.0 is advertised or if other routes can also be specified.
To advertise network 0.0.0.0 to DVMRP neighbors on an interface, use the following command in
interface configuration mode:
Advanced DVMRP Interoperability Configuration Task List
Cisco routers run PIM and know enough about DVMRP to successfully forward multicast packets to
receivers and receive multicast packets from senders. It is also possible to propagate DVMRP routes into
and through a PIM cloud. PIM uses this information; however, Cisco routers do not implement DVMRP
to forward multicast packets.
The basic DVMRP interoperability features are described in the section “Basic DVMRP Interoperability
Configuration Task List” earlier in this chapter. To configure more advanced DVMRP interoperability
features on a Cisco router, perform the optional tasks described in the following sections:
• Enabling DVMRP Unicast Routing (Optional)
• Limiting the Number of DVMRP Routes Advertised (Optional)
• Changing the DVMRP Route Threshold (Optional)
• Configuring a DVMRP Summary Address (Optional)
• Disabling DVMRP Automatic summarization (Optional)
• Adding a Metric Offset to the DVMRP Route (Optional)
• Rejecting a DVMRP Nonpruning Neighbor (Optional)
• Configuring a Delay Between DVRMP Reports (Optional)
Enabling DVMRP Unicast Routing
Because policy for multicast routing and unicast routing requires separate topologies, PIM must follow
the multicast topology to build loopless distribution trees. Using DVMRP unicast routing, Cisco routers
and mrouted machines exchange DVMRP unicast routes, to which PIM can then reverse path forward.
Cisco routers do not perform DVMRP multicast routing among each other, but they can exchange
DVMRP routes. The DVMRP routes provide a multicast topology that may differ from the unicast
topology. These routes allow PIM to run over the multicast topology, thereby allowing PIM sparse mode
over the MBONE topology.
Command Purpose
Router(config-if)# ip dvmrp default-information
{originate | only}
Advertises network 0.0.0.0 to DVMRP neighbors.