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Routing & Switching · Advanced

Bidirectional PIM (Bidir-PIM)

A PIM variant with only shared trees where traffic flows up and down the tree to the RP, suited to many-to-many applications.

Definition

Bidir-PIM avoids (S,G) state and register messages, scaling well when many sources exist. A designated forwarder (DF) is elected on each link to prevent loops instead of RPF checks per source.

Example

ip pim rp-address 10.0.0.1 bidir

Exam tip

Bidir uses a designated forwarder, not per-source RPF, and never builds source trees.

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