Multicast:Please confirm my approach for this multicast scenario

Unanswered Question
Nov 20th, 2009

Hello folks,

Please find attached sketch outlining topology.

I would like to confirm if enabling PIM-SPARSE and making each of the spoke routers as RP for the respective sites is the right approach to solve this? Also, in case you are aware of better techniques using perhaps multicast services from the Service Provider, please let me know.

Consider that WAN links are 3xT1.

I have this problem too.
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Mohamed Sobair Fri, 11/20/2009 - 09:36

Hi,

I would choose the approach  to have CAT 6500 is the RP for all the Groups of the muticast traffic as its closes to the Source. keep in mind 6500 is a single point of failure since its the only device connecting service provider and the multicast server (Inline). I would have another RP as backup with the 6500 if applicable.

Service provider multicast is totally transparent from the customer multicast traffic.

The Service provider technique uses  tunnels between PEs to forward multicast, unlike GRE tunnels , this is not apoint to point tunnel, this tunnel creates Multicast tunnel interface and unicast the multicast packet to the remote PE. CEs signal the use of DATA-MDT through port 3232 UDP, Only CEs intend recipient of Data. A uniqe Group at the service provider is required, a unique source is also required , this source recommended to be the Looback interface of the originating BGP LDP session. Service provider uses Dense mode to forward pim control messages, Only Pim Sparse mode is allowed, Pim bidirectional will be considered as soon as it prooves stability.

So from the customer prespective, all Bootstrab messages , pim dense , pim sparse traffic is transparent as its forwarded by the service provider.

On the LAN, I would definately configure IGMP snooping on each site to optimize multicast traffic and reuce un necessary Multicast waste bandwidth.

HTH

Mohamed

news2010a Fri, 11/20/2009 - 10:54

Great.
One more question:

If I make the 6500 as the RP, would you use static RP?
Or would you configure bootstrap (I understand that is a very good option for discovery of automatic RP instead of  Cisco auto-RP).

Giuseppe Larosa Fri, 11/20/2009 - 09:46

Hello Marlon,

as Mohamed has explained very well you should be able to have your C6500 as the RP for all sites if your service provider has implemented multicast VPN options.

So this is the first check to perform consult documentation provided by them about what services they are providing to you.

if multicast VPN service is not enabled you should consider to ask them an offer for this service.

without multicast VPN enabled on server side you should tunnel multicast traffic over GRE tunnels and it requires work and can cause performance issues.

Hope to help

Giuseppe

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