Cisco Systems 3750E manual Rejecting a Dvmrp Nonpruning Neighbor, 42-45

Chapter 42 Configuring IP Multicast Routing

Configuring Advanced DVMRP Interoperability Features

Rejecting a DVMRP Nonpruning Neighbor

By default, Cisco devices accept all DVMRP neighbors as peers, regardless of their DVMRP capability. However, some non-Cisco devices run old versions of DVMRP that cannot prune, so they continuously receive forwarded packets, wasting bandwidth. Figure 42-7shows this scenario.

Figure 42-7 Leaf Nonpruning DVMRP Neighbor

Source router or RP
RP	PIM dense mode

Router A

Valid	Router B
multicast		Receiver
traffic

	Layer 3 switch
Unnecessary
multicast
traffic
Leaf nonpruning
DVMRP device		101244
Stub LAN with no members

You can prevent the switch from peering (communicating) with a DVMRP neighbor if that neighbor does not support DVMRP pruning or grafting. To do so, configure the switch (which is a neighbor to the leaf, nonpruning DVMRP machine) with the ip dvmrp reject-non-prunersinterface configuration command on the interface connected to the nonpruning machine as shown in Figure 42-8. In this case, when the switch receives DVMRP probe or report message without the prune-capable flag set, the switch logs a syslog message and discards the message.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		42-45