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Multicast SSM question


i have an MPLS backbone which is running sparse-mode. and i am trying to support Multicast for VRF's.. whats happening at the moment is when i configure MDT. The tunnels come up properlly. end to end ping works fine . but for only 1 icmp echo request. i get th response for first packet. after that packets aregetting dropped and i am getting no response.

any ideas ?

can i use SSM mode in conjunction with sparse-mode ?



Cisco Employee

Re: Multicast SSM question


It is hard to say what can be wrong without more information. Can you explain what you mean when you say you can ping end to end.

As far as you second question is concerned, there is no concept of dense-mode with SSM, so the answer is yes, you can run SSM with the interface configured for sparse-mode.


Harold Ritter
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New Member

Re: Multicast SSM question

Hi ,

i have a customer their head office has dual home connectivity to 2 PE devices and then i have a remote site.

within backbone network we have sparse mode running. with bsr .. within customer network they have static RP configured.

The head office is RP.

Now what happens is when i configure MDT on all 3 PE devices . the tunnel comes up and i can see them as PI peer for that VRF.

if there is any server at remote site and clients at head office . it just doesnt work. only 1 packet of ping is going through.

on the other hand if there are multicast clients on the remote site and server in head office . that works fine. no dramas.

i hope this explains .. but if you still need some more information . i can create a diagram and send it over to you.




Re: Multicast SSM question

amit i can think of a thousand reasons why this could happen. Can you post actual configs of the PE multicast and the CE multicast. Please include pim neighbours and ip mroute if possible. Also a show on the mdt (i cant remember the command as its been too long). First thing that springs to mind is the default mdt is working then it kicks in to the data mdt and this is when you get the issue. RPF check - are your loopbacks being advertised properly?

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