Cisco Systems 78-11741-02 manual Rejecting a Dvmrp Nonpruning Neighbor, IPC-543

Configuring DVMRP Interoperability

Advanced DVMRP Interoperability Configuration Task List

Rejecting a DVMRP Nonpruning Neighbor

By default, Cisco routers accept all DVMRP neighbors as peers, regardless of their DVMRP capability or lack of. However, some non-Cisco machines run old versions of DVMRP that cannot prune, so they will continuously receive forwarded packets unnecessarily, wasting bandwidth. Figure 93 shows this scenario.

Figure 93 Leaf Nonpruning DVMRP Neighbor

Source or RP

RP PIM dense mode

		Router A
	Valid	Router B
multicast
			Receiver
traffic
		Router C

Wasted
multicast
traffic
Leaf nonpruning
DVMRP machine	43276
Stub LAN with no members

You can prevent a router from peering (communicating) with a DVMRP neighbor if that neighbor does not support DVMRP pruning or grafting. To do so, configure Router C (which is a neighbor to the leaf, nonpruning DVMRP machine) with the ip dvmrp reject-non-prunersinterface configuration command on the interface to the nonpruning machine. Figure 94 illustrates this scenario. In this case, when the router receives a DVMRP probe or report message without the Prune-Capable flag set, the router logs a syslog message and discards the message.

Cisco IOS IP Configuration Guide

IPC-543