Cisco Systems 78-11741-02 manual Configuring Dvmrp Interoperability, Responding to mrinfo Requests

Configuring DVMRP Interoperability

Basic DVMRP Interoperability Configuration Task List

Configuring DVMRP Interoperability

Cisco multicast routers using PIM can interoperate with non-Cisco multicast routers that use the

DVMRP.

PIM routers dynamically discover DVMRP multicast routers on attached networks. Once a DVMRP neighbor has been discovered, the router periodically sends DVMRP report messages advertising the unicast sources reachable in the PIM domain. By default, directly connected subnets and networks are advertised. The router forwards multicast packets that have been forwarded by DVMRP routers and, in turn, forwards multicast packets to DVMRP routers.

You can configure which sources are advertised and which metrics are used by configuring the ip dvmrp metric interface configuration command. You can also direct all sources learned via a particular unicast routing process to be advertised into DVMRP.

The mrouted protocol is a public-domain implementation of DVMRP. It is necessary to use mrouted Version 3.8 (which implements a nonpruning version of DVMRP) when Cisco routers are directly connected to DVMRP routers or interoperate with DVMRP routers over an multicast backbone (MBONE) tunnel. DVMRP advertisements produced by the Cisco IOS software can cause older versions of mrouted to corrupt their routing tables and those of their neighbors. Any router connected to the MBONE should have an access list to limit the number of unicast routes that are advertised via DVMRP.

To configure the sources that are advertised and the metrics that are used when DVMRP report messages are sent, use the following command in interface configuration mode:

Command	Purpose
Router(config-if)# ip dvmrp metric metric [list	Configures the metric associated with a set of destinations for
access-list] [protocol process-id]	DVMRP reports.

A more sophisticated way to achieve the same results as the preceding command is to use a route map instead of an access list. Thus, you have a finer granularity of control. To subject unicast routes to route map conditions before they are injected into DVMRP, use the following command in interface configuration mode:

Command	Purpose
Router(config-if)# ip dvmrp metric metric	Subjects unicast routes to route map conditions before they are
[route-map map-name]	injected into DVMRP.

Responding to mrinfo Requests

The Cisco IOS software answers mrinfo requests sent by mrouted systems and Cisco routers. The software returns information about neighbors on DVMRP tunnels and all of the interfaces of the router. This information includes the metric (which is always set to 1), the configured TTL threshold, the status of the interface, and various flags. The mrinfo EXEC command can also be used to query the router itself, as in the following example:

mm1-7kd# mrinfo

171.69.214.27 (mm1-7kd.cisco.com) [version cisco 11.1] [flags: PMS]: 171.69.214.27 -> 171.69.214.26 (mm1-r7kb.cisco.com) [1/0/pim/querier] 171.69.214.27 -> 171.69.214.25 (mm1-45a.cisco.com) [1/0/pim/querier] 171.69.214.33 -> 171.69.214.34 (mm1-45c.cisco.com) [1/0/pim] 171.69.214.137 -> 0.0.0.0 [1/0/pim/querier/down/leaf]

Cisco IOS IP Configuration Guide

IPC-538