[j-nsp] Multicast

[Jee Kay]

I've got a really strange problem with multicast between a pair of
Junipers. The setup is as follows:

Traffic Generator -- Juniper1 -- Juniper2 -- Traffic Sink

The two Junipers see each other as PIM neighbours happily. Juniper1
seems a PIM Join entry for the Sink, and the output of show pim join
extensive and show multicast route says it is correctly forwarding the
multicast traffic out towards Juniper2.

Juniper2, in turn, has a PIM Join entry correctly showing that traffic
should be sent towards the sink, aswell as the appropriate IGMP Group
entry. Show multicast route on this route says no route entries
matched.

As far as I can tell from a sniffer between J1 and J2, the multicast
traffic is genuinely appearing on the link, although a filter on the
ingress interface on J2 doesn't seem to pick it up.

Anyone have any ideas how to go about troubleshooting exactly what's
happening here? It looks like all the individual components are
working correctly but there is some key part missing that is causing
J2 to receive the multicast but not realise that, despite the IGMP
state, it needs forwarding on.

For the record, this is all PIM Sparse, J1 is the RP (set as local on
J1, static on J2), I am using inet.2 for RPF checks (with the
appropriate rib-groups to distribute OSPF into .0 and .2), have
interface-routes set to distribute into both tables also. IGMP is
enabled on all interfaces, version 2. Packet traces show that the sink
is correctly using IGMPv2. PIM is also enabled on all interfaces, mode
sparse. The RP address is a secondary IP on lo0 of J1. PIM and IGMP
are disabled on fxp0.

Thanks in advance,
Ras