46-54
Catalyst 3750 SwitchSoftware Configuration Guide
OL-8550-09
Chapter46 Configuring IP Multicast Routing
Configuring Advanced DVMRP Interoperability Features
These sections contain this configuration information:
Enabling DVMRP Unicast Routing, page 46-54 (optional)
Rejecting a DVMRP Nonpruning Neighbor, page46-55 (optional)
Controlling Route Exchanges, page 46-57 (optional)
For information on basic DVMRP features, see the “Configuring Basic DVMRP Interoperability
Features” section on page46-48.
Enabling DVMRP Unicast Routing
Because multicast routing and unicast routing require separate topologies, PIM must follow the
multicast topology to build loopless distribution trees. Using DVMRP unicast routing, Cisco routers,
multilayer switches, and mrouted-based machines exchange DVMRP unicast routes, to which PIM can
then reverse-path forward.
Cisco devices do not perform DVMRP multicast routing among each other, but they can exchange
DVMRP routes. The DVMRP routes provide a multicast topology that might differ from the unicast
topology. This enables PIM to run over the multicast topology, thereby enabling sparse-mode PIM over
the MBONE topology.
When DVMRP unicast routing is enabled, the router or switch caches routes learned in DVMRP report
messages in a DVMRP routing table. When PIM is running, these routes might be preferred over routes
in the unicast routing table, enabling PIM to run on the MBONE topology when it is different from the
unicast topology.
DVMRP unicast routing can run on all interfaces. For DVMRP tunnels, it uses DVMRP multicast
routing. This feature does not enable DVMRP multicast routing among Cisco routers and multilayer
switches. However, if there is a DVMRP-capable multicast router, the Cisco device can do PIM/DVMRP
multicast routing.
Beginning in privileged EXEC mode, follow these steps to enable DVMRP unicast routing. This
procedure is optional.
To disable this feature, use the no ip dvmrp unicast-routing interface configuration command.
Command Purpose
Step1 configure terminal Enter global configuration mode.
Step2 interface interface-id Specify the interface that is connected to the DVMRP router, and enter
interface configuration mode.
Step3 ip dvmrp unicast-routing Enable DVMRP unicast routing (to send and receive DVMRP routes).
This feature is disabled by default.
Step4 end Return to privileged EXEC mode.
Step5 show running-config Verify your entries.
Step6 copy running-config startup-config (Optional) Save your entries in the configuration file.