Configuring Dvmrp Interoperability - Cisco Catalyst 3550 series Software Configuration Manual

Configuring Basic DVMRP Interoperability Features

Configuring DVMRP Interoperability

Cisco multicast routers and multilayer switches using PIM can interoperate with non-Cisco multicast
routers that use the DVMRP.
PIM devices dynamically discover DVMRP multicast routers on attached networks by listening to
DVMR probe messages. When a DVMRP neighbor has been discovered, the PIM device periodically
sends DVMRP report messages advertising the unicast sources reachable in the PIM domain. By default,
directly connected subnets and networks are advertised. The device forwards multicast packets that have
been forwarded by DVMRP routers and, in turn, forwards multicast packets to DVMRP routers.
DVMRP interoperability is automatically activated when a Cisco PIM device receives a DVMRP probe
message on a multicast-enabled interface. No specific Cisco IOS command is configured to enable
DVMRP interoperability; however, you must enable multicast routing. For more information, see the
"Configuring Basic Multicast Routing" section on page
Controlling Unicast Route Advertisements
You should configure an access list on the PIM routed interface connected to the MBONE to limit the
number of unicast routes that are advertised in DVMRP route reports; otherwise, all routes in the unicast
routing table are advertised.
Note The mrouted protocol is a public-domain implementation of DVMRP. You must use mrouted Version 3.8
(which implements a nonpruning version of DVMRP) when Cisco routers and multilayer switches are
directly connected to DVMRP routers or interoperate with DVMRP routers over an MBONE tunnel.
DVMRP advertisements produced by the Cisco IOS software can cause older versions of the mrouted
protocol to corrupt their routing tables and those of their neighbors.
You can configure what sources are advertised and what metrics are used by configuring the ip dvmrp
metric interface configuration command. You can also direct all sources learned through a particular
unicast routing process to be advertised into DVMRP.
Catalyst 3550 Multilayer Switch Software Configuration Guide
34-44
Chapter 34 Configuring IP Multicast Routing
34-15.
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