multicast problem

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Jan 1st, 2009
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guys i am pretty new to multicast i have two question if someone can kindly answer it....1. when we put ip pim nbma mode (which type of FR connection) or we have to put it on every FR interface regardless of point to point or multipoint etc.....second thing is how we config DR inface what is the concept of DR in multicasting.....thanks guys for looking

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Giuseppe Larosa Thu, 01/01/2009 - 06:28
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Hello Khan,

PIM DR: Designated Router in a LAN segment PIM routers elect a Designated Router that is the one with the highest IP address on the LAN subnet.

the PIM DR will represent the segment towards the rest of the network for both sources and receivers.

Be aware of these other two concepts:

IGMP querier the router that sends out IGMP queries every 60 seconds (lowest ip address in subnet with IGMP vers. 2 or later)

Designated Forwarder: the router that will really put on the lan traffic for a group (this is group specific) for which at least one receiver exists

By using the PIM assert messages the routers compare to see who is better connected to the group source, the winner should be the only to send out traffic for the group

= to have its interface in the oilist for the group

ip pim nbma mode : this is a detail study before PIM on the LANS and the different types of PIM: PIM SM , PIM DM, PIM SSM, bidirectional PIM

Happy new year

Hope to help


steve_steele Thu, 01/01/2009 - 15:11
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pim nbma mode is used for multipoint nbma interfaces.

pim normally maintains a database of (source / group) entries detailing which interface to send multicast traffic out of.

If your frame relay connection is point to point then specifying which interface to forward the multicast traffic out of is sufficient and nbma mode is not required.

If your frame relay uses multipoint interfaces and you have a requirement that multicast traffic coming in one multipoint interface be sent out the same interface to a different site then you will need nbma mode. It adds an ip address to the database entry to differentiate between multiple sites out the same interface.

Not sure what your asking in reference to the DR, but you can have multiple sources for the same group.




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