Multicast mVPN


This page describes the mVPN architecture.

Multicast Domain Overview

  • mVRF - Multicast VRFs.
  • GRE Tunnels - Point to multipoint GRE tunnels created from PE to PEs. Destination is a multicast group.
  • MDTs - Multicast Distribution Trees.
    • Default MDT
    • Data MDT
  • PIM Adj - PIM adj is between CE-PE and PE-PE.
  • MTI Interface - Multicast Tunnel Interface, which represents the GRE tunnel.
  • RFP Check - Reverse Forwarding Path check used by multicast forwarding to prevent loops.
  • mVPN Forwarding
    • C-PIM - multicast forwarding for multicast packets from CE to PE.
    • P-PIM - multicast forwarding for multicast packets from PE to P.


  • Used to maintain all of the customer multicast states.
  • PEs maps all customer groups into one multicast group for each mVRF called Default-MDT.
  • Each mVRF belongs to a Default-MDT (Under vrf definition mdt default 239.x.x.x).
  • Multicast feature and protocols mVRF aware include:
    • PIM
    • IGMP
    • MSDP

GRE Tunnels (MTI)

  • Source of the tunnels it the BGP source address.
  • Destination of the tunnel is the customer specific multicast address.

MDT (Default and Data)

  • Multicast tunnels used on the MPLS Core.
  • Default MDT -
  • Data MDT -


  • There is a number of PIM adj within the mVPN network.
  • First one is between CE and PE.
  • Another one is using the MTI interface with other PEs that have are part of the same mVPN domain.
  • The same PIM instance is used for each mVPN domain between the CE-PE and PE-PE based on associated mVPNs. For example CE-PE of mVPN1 will use the same instance for PE1 and PE2 that have mVPN1 configured.

RFP Check

mVPN Forwarding (C and P-PIM)

  • Requires the command ip multicast-forwarding vrf X.


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