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Routing & Switching · Intermediate

Protocol Independent Multicast (PIM)

The family of multicast routing protocols that build distribution trees using the existing unicast routing table for RPF checks.

Definition

PIM does not exchange routes itself; it relies on any unicast protocol, hence 'protocol independent'. Modes are Dense Mode (flood and prune), Sparse Mode (explicit join to an RP), Source-Specific Multicast and Bidirectional. PIMv2 uses IP protocol 103 and 224.0.0.13.

Example

ip multicast-routing ; interface Gi0/0 / ip pim sparse-mode

Exam tip

PIM needs ip multicast-routing enabled globally on Cisco IOS, a common missed step.

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