Cisco Systems 3750E manual Configuring Dvmrp Interoperability, 42-39

Chapter 42 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 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.

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.

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	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	access-listaccess-list-number {deny	Create a standard access list, repeating the command as many times as
	permit} source [source-wildcard]	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.
Step 3
	interface interface-id	Specify the interface connected to the MBONE and enabled for
		multicast routing, and enter interface configuration mode.

	Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02		42-39