Cisco Systems 3750E manual Enabling Dvmrp Unicast Routing, 42-44

Chapter 42 Configuring IP Multicast Routing

Configuring Advanced DVMRP Interoperability Features

These sections contain this configuration information:

•Enabling DVMRP Unicast Routing, page 42-44(optional)

•Rejecting a DVMRP Nonpruning Neighbor, page 42-45(optional)

•Controlling Route Exchanges, page 42-47(optional)

For information on basic DVMRP features, see the “Configuring Basic DVMRP Interoperability Features” section on page 42-38.

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.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify the interface that is connected to the DVMRP router, and enter
		interface configuration mode.
Step 3
	ip dvmrp unicast-routing	Enable DVMRP unicast routing (to send and receive DVMRP routes).
		This feature is disabled by default.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show running-config	Verify your entries.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To disable this feature, use the no ip dvmrp unicast-routinginterface configuration command.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
42-44	OL-9775-02