Cisco APIC Layer 3 Networking Configuration Guide, Release 6.2(x)

PIM/PIM6 designated router election

Updated: April 17, 2026

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Explains the PIM/PIM6 designated router election mechanism for different interface types in Layer 3 IPv4/IPv6 multicast on ACI fabric.

PIM/PIM6 designated router election is a multicast routing mechanism that determines which router becomes the designated router for different interface types in Layer 3 IPv4/IPv6 multicast on ACI fabric.

Interface types and DR election behavior

The PIM/PIM6 DR election mechanism varies by interface type:

PIM/PIM6-enabled L3 Out interfaces: Follows standard PIM/PIM6 DR mechanism in these types of interfaces.
Fabric interface: DR election on this interface is not of much significance as the DR functionality is determined by the striping. PIM/PIM6 DR election continues unaltered on this interface.
IPv4/IPv6 multicast routing-enabled pervasive BDs: The pervasive BDs in the fabric are all stubs with respect to IPv4/IPv6 multicast routing. Hence, on all the leaf switches, the SVI interfaces for pervasive BDs including vPC, are considered DR on the segment.

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