[c-nsp] CGMP question

[Bernie]

Hello! I'm new to working with CGMP and PIM in general and have a
conundrum-

I've come into a new network where multicast is configured. There is no
experienced network engineer on site with historical info on this setup.

I believe CGMP is misconfigured because taking my personal laptop and
connecting it to a user port shows roughly 75% of the packets received
(600/800) in 30 seconds are CGMP Join messages (Wireshark pcap).

The core 6500 switch is configured as follows-

  ip pim rp-address x.x.x.x 85
  ip pim send-rp-announce LoopbackXX scope 16 group-list 85 interval 30

interface LoopbackXX
  description PIM RP loopback IP
  ip address x.x.x.x y.y.y.y
  ip pim sparse-dense mode

Interface Vlan55
  description User Vlan
  ip pim sparse-dense-mode
  ip cgmp
  no ip mroute-cache

>From the core it's layer 2 out to edge switches (3750 stacks) on the user
vlan. I don't see any explicit configs on the 3750 stacks so I'm thinking
that's where my problem is, but I don't know how to proceed!

Regards,

Bernie

-- 
A politician is an animal which can sit on a fence and yet keep both ears
to the ground. -H.L. Mencken