Rejecting A Dvmrp Nonpruning Neighbor - Cisco Catalyst 3750 Software Configuration Manual

Chapter 31 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 31-6 shows this scenario.
Figure 31-6 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
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-pruners interface configuration command
on the interface connected to the nonpruning machine as shown in Figure 31-7. 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 Metro Switch Software Configuration Guide
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