Avaya Configuring IP Multicasting and Multimedia Services Manual do Utilizador descarregar pdf (Página 61)

Customizing DVMRP

303527-A Rev. 00

4-5

How DVMRP Chooses a Route

Each DVMRP interface is configured with a metric that indicates the cost of the

hop. A router that receives multiple route reports for the same multicasting source

network:

• Compares the cost specified in each (based on the metric field)

• Stores information from the report with the lowest cost in its routing table

A route metric is the sum of all the interface (hop) metrics from a given route

source to a given router.

In Figure 4-1

on page 4-3, for example, router D receives two reports for the

network connected to multicasting router A, one from router B and one from

router C. Using the metrics contained in the route reports, router D determines that

the cost of the tunneled route is greater than the cost of the route that uses direct

physical connections. Router D discards the route received from router C and

stores the route received from router B.

Router D then declares router B to be the next-hop neighbor and interface d1 to be

the next-hop interface. After a next-hop neighbor has been declared for a route,

the route updates received from that neighbor for that route take precedence until

either the route times out or until another router advertises a better metric for that

route.

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Avaya Configuring IP Multicasting and Multimedia Services Manual do Utilizador Página 61