[c-nsp] Cat4500/Sup5 not forwarding local multicast

[Ras]

I currently have a problem where a Cat4500/Sup5 is not forwarding
multicast where both the source and destination networks are locally
attached. A 'show ip mroute count' gives this:

cat4500-sup5#sh ip mro mcast-group src-ip count
IP Multicast Statistics
685 routes using 631462 bytes of memory
154 groups, 3.44 average sources per group
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: mcast-group, Source count: 44, Packets forwarded: 901267197,
Packets received: 944510033
  Source: src-ip/32, Forwarding: NC/NC/NC/NC, Other: NC/NC/NC



A 'show ip mroute' for this source gives:

cat4500-sup5#sh ip mro mcast-group src-ip
IP Multicast Routing Table
Flags: D - Dense, S - Sparse, B - Bidir Group, s - SSM Group, C - Connected,
       L - Local, P - Pruned, R - RP-bit set, F - Register flag,
       T - SPT-bit set, J - Join SPT, M - MSDP created entry,
       X - Proxy Join Timer Running, A - Candidate for MSDP Advertisement,
       U - URD, I - Received Source Specific Host Report,
       Z - Multicast Tunnel, z - MDT-data group sender,
       Y - Joined MDT-data group, y - Sending to MDT-data group
Outgoing interface flags: H - Hardware switched, A - Assert winner
 Timers: Uptime/Expires
 Interface state: Interface, Next-Hop or VCD, State/Mode

(src-ip, mcast-group), 00:01:31/00:02:13, flags: T
  Incoming interface: Vlan251, RPF nbr 0.0.0.0
  Outgoing interface list:
    Vlan665, Forward/Sparse-Dense, 00:01:31/00:02:59, H
    Vlan250, Forward/Sparse, 00:01:31/00:02:56, H


For some reasons these (S,G) entries are very young - they should have
been active for at least a week. It seems like the entry is cycling
roughly once every 180 seconds but I can find no obvious cause.

Anyone have any ideas on what NC/NC/NC might mean or why this would be
happening?

Thanks,
Ras