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Multicast over Unicast WAN via GRE tunnels for VoD

Hi peps

I am need of a little assistance. I am woring on a kludge to get multicast to work over our BT MPLS WAN. BT do not support multicast on our WAN service so I am thinking of using a few GRE tunnels to 'hide' it from them.

We opperate a fully MPLS LAN environment over multiple sites connected by a BT MPLS WAN service. We are not passing lables to the SP or to other sites. Each site is their own MPLS environment opperating their own private AS. The CEs are their own AS.

MPLS LAN -> IP-CE -> MPLS WAN -> IP-CE -> MPLS LAN

65535 -> 64535 -> 2856 -> 64520 -> 65520

The LAN vrfs are already enabled for multicast, using PIM spare-modet. Each site has their own Anycast RP. The application in question is non-deterministic and any unicast host can become the multicast source!

I was thinking of adding a GRE tunnel interface between the two LAN PEs and create an MSDP peering between the LAN RPs.

MTU and QoS issues aside, my question is:

1) How do I get the multicast traffic to go over the tunnel interface and leave the unicast traffic as is?

2) If so, I expect to run into RPF issues, right?

     I know I can add static mroutes to get round these issues but is their a scalable way to resolve this, especially as I dont know which machine is source and this can change rapidly?

I hope this all makes sence! I've not had a chance to lab this up yet.

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Re: Multicast over Unicast WAN via GRE tunnels for VoD

James,

If you don't want your mcast flows to follow the unicast, you have 2 options.

Either mroute or BGP Extension for Multicast.

You can configure BGP peering via the GRE tunnel and just active the Multicast extension.

This will prevent learning unicast routes from BGP neighbors while having some kind of dynamic mrouting in your network.

Something like:

router bgp xx

neighbor 1.1.1.1 remote xx

address-family ipv4 unicast

no neighbor 1.1.1.1 activate

address-family ipv4 multicast

neighbor 1.1.1.1 activate

network x.x.x.x (source IP subnet)

Be sure to lab this theory up.

Regards,

Edison

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