Cisco Catalyst 3120 User Manual

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Cisco Catalyst Blade Switch 3120 for HP Software Configuration Guide
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Chapter 44 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 44-7 shows this scenario.
Figure 44-7 Leaf Nonpruning DVMRP Neighbor
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 44-8. 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.
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Router A
Router B
Layer 3 switch
RP
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multicast
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Source router or RP
PIM dense mod
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Leaf nonpruning
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Receive
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Stub LAN with no members

Cisco Catalyst 3120 Specifications

General

Brand	Cisco
Model	Catalyst 3120
Category	Switch
Language	English