Hey Michael,

I'm pretty certain you won't get a PIM adjacency up over a frame PVC that
does not have pseudo-broadcast enabled. PIM uses 224.0.0.13 for neighbor
discovery. And the multicast packets that PIM is routing most definitely
need a broadcast-enabled frame PVC.

The 'ip pim nbma-mode' is not related to whether PIM uses link-local
multicast for neighbor discovery, rather it is used to deal with potential
RPF issues in a frame-relay hub and spoke network. If the hub receives a
multicast packet from a spoke off of the frame-relay link on Serial1/0, for
example, it would not be able to forward that same packet back out to
another spoke neighbor off the same interface as the interface the packet
was received on (the RPF interface) cannot be included in the OIL for the
group (as that would indicate an automatic RPF violation).

'ip pim nbma-mode' simply allows the router to include the actual PIM
neighbor ID rather than the interface in the OIL so that the router can
"hairpin" the multicast packet and send it back out to spokes other than
the one it was received by.

Can you get PIM and multicast across a non-broadcast frame-relay link? Sure
-- that's what tunnels are for ;-)

Good luck on your lab!


On Thu, Mar 21, 2013 at 12:03 AM, Michael Davis - Webquor <
[email protected]> wrote:

> Hi everyone – I am working on multicast which is my biggest weakness
> leading up to the lab next week.  I am trying to get a PIM adjacency over a
> non broadcast frame-relay connection.  It is not coming up.  Can someone
> please explain if it is possible and why the command "ip pim nbma-mode" is
> necessary on non-broadcast networks?  The command doesn't seem to do
> anything to be honest.  I suppose the big question is can I establish a PIM
> adjacency over a frame-relay connection where no broadcast capability is
> enabled?
>
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