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Chapter 44
Configuring IP Multicast Routing
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.
You can 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.
The mrouted protocol is a public-domain implementation of DVMRP. You must use mrouted
Note
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.
Beginning in privileged EXEC mode, follow these steps to configure the sources that are advertised and
the metrics that are used when DVMRP route-report messages are sent. This procedure is optional.
Command
Step 1
configure terminal
Step 2
access-list access-list-number {deny |
permit} source [source-wildcard]
Step 3
interface interface-id
OL-12247-04
Purpose
Enter global configuration mode.
Create a standard access list, repeating the command as many times as
necessary.
For access-list-number, the range is 1 to 99.
•
The deny keyword denies access if the conditions are matched. The
•
permit keyword permits access if the conditions are matched.
For source, enter the number of the network or host from which the
•
packet is being sent.
(Optional) For source-wildcard, enter the wildcard bits in dotted
•
decimal notation to be applied to the source. Place ones in the bit
positions that you want to ignore.
Recall that the access list is always terminated by an implicit deny
statement for everything.
Specify the interface connected to the MBONE and enabled for
multicast routing, and enter interface configuration mode.
Cisco Catalyst Blade Switch 3130 and 3032 for Dell Software Configuration Guide
Configuring Basic DVMRP Interoperability Features
44-49
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