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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter24 Configuring IP Multicast Routing
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 d iscov er ed, th e PIM d ev ice p eri odic ally
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 tha t have
been forwarded by DVMRP routers and, in turn, forwards mu ltic a st pa cket s to DV M RP rout ers.
DVMRP interoperability is automatically activated when a Cisco PIM device receives a DVMRP probe
message on a multicast-enabled interface. No specific 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 24-1 5.
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 DVM RP route reports; otherwise, all routes in the unicast
routing table are advertised.
Note The mrouted protocol is a public-domain implementati on of D V MRP. You must use mrouted
Version3.8 (which impleme nts 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 throu gh a part ic ular
unicast routing process to be advertised into DVMRP.