Configuring DVMRP Interoperability
Advanced DVMRP Interoperability Configuration Task List
IPC-543
Cisco IOS IP Configuration Guide
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. Figure93 shows this
scenario.
Figure93 Leaf Nonpruning DVMRP Neighbor
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-pruners interface 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.
Router A
Router B
Router C
RP
Valid
multicast
traffic
Wasted
multicast
traffic
43276
Source or RP
PIM dense mode
Leaf nonpruning
DVMRP machine
Receiver
Stub LAN with no members