multicast/mdt/mVPN - BGP Address Families

I've yet to find a really good write-up of what the various BGP multicast address families are for and to which feature they apply.  Can anyone provide a good reference for that? I know what some of them do but honestly, I don't have a firm grasp on when to use each one.

Router(config-router)#address-family ipv4 ?

  mdt        Address Family modifier

  multicast  Address Family modifier

  mvpn       Address Family modifier

  unicast    Address Family modifier

  vrf        Specify parameters for a VPN Routing/Forwarding instance


Router(config-router)#address-family ipv4

Router(config-router)#address-family vpnv4 ?

  multicast  Address Family modifier

  unicast    Address Family Modifier


Router(config-router)#address-family vpnv4

Specifically, I like to know about:

ipv4 multicast

ipv4 mdt

ipv4 mvpn

vpnv4 multicast

What goes on PE and what goes on CE?  

Sorry for the wide open question.  

thank you.


  • peetypeety ✭✭✭

    vpnv4 goes on PE. It's the mechanism for transfering VPNv4 routes (aka the 96-bit routes, made up of 48-bit RD, 16-bits of magic, and 32-bits of v4 route from within the VRF, plus a mask, probably with one or more extended communities that match the RT export(s)) from one PE to another PE, potentially by way of P routers and/or route reflectors, etc.

    ipv4 vrf <blah> goes on PE. It's the mechanism for getting CE/BGP routes over to vpnv4 land, plus a place to redistribute CE/EIGRP, CE/ISIS, CE/OSPF, CE-facing-static, and PE-CE-connected routes into VRF and VPNv4 land.

    Does that help at all?

  • It helps a little but I want to get the specifics of when to use which address family.

    for example, which address family is for LSM?  which is for Rosen GRE?  Which if for BGP multicast signalling?  etc...  


    thanks for the reply!

  • my understanding of them is basically this:
    ipv4 multicast = advertises regular multicast RPF information.
    ipv4 mdt  =  advertises MDT info for mcast VPNs (PIM in the SP core).
    ipv4 mvpn =  NG MVPN / C-signaling via BGP.

    So anytime you want to send default/data MDT info in BGP, you'd use MDT SAFI.

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