Question on Multicast - MPLS

Unanswered Question
Aug 3rd, 2010

Imagine one has

HeadquarterCE---------(PE1 MPLS PE2)----------CEBranch1

(Source)                                                        (Receiver)

From reading the documentation below, I see the associated configuration that service provider would do in order to make PE and P routers as PIM neigbhors.

From a customer perspective, what are the configurations left for the CE routers?

I mean, I am just trying to understand how using multicast implemented on the MPLS network will save work and configuration time for customers.

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Giuseppe Larosa Wed, 08/04/2010 - 01:02

Hello Marlon,

CE nodes need to have ip multicast routing enabled and PIM on the interfaces towards the PE nodes.

Eventually MSDP is needed if RP is deployed on a customer device.

SP will interconnect customer PIM islands

the savings are :

customer doesn't need to use a mesh of GRE tunnels to carry multicast flows between the different sites over unicast L3 VPN or to use dedicated links (different from L3 VPN access links) to route multicast traffic

As you see it makes some difference.

Hope to help


news2010a Wed, 08/04/2010 - 09:10


Do you know if typically on the Service Provider MPLS (PE and P routers) you see RP's deployed or service providers are using SSM (IGMPv3)? (that means, no RP configuration required)

Giuseppe Larosa Wed, 08/04/2010 - 12:20

Hello Marlon,

your understanding is correct: PIM SSM should be the preferred choice on SP side as it allows to skip RP configuration in VRF or to use MSDP towards customer RP.

However, the customer may be still using PIM SM with RP(s)

Hope to help



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