We have a small school with a 3550 L3 with IGMP, 4500 series with IGMP and 2 3500xl off the 3550 with CGMP. Multicasting doesn't seem to work at all. Snooping is enabled on all. but, on the 3500 series, no groups or router is listed.
can IGMP and CGMP work with each other?
they can interoperate and are supposed to in environments that require it.
ie: CGMP (cisco proprietary) enables a cisco multicast router to understand IGMP messages and informs the switch of the info. in the IGMP message.
there could be quite a few reasons your Mcast is not operating as expected.
from the PIM mode configuration to no ip path.
please see the following link for more info on IGMP and CGMP interoperation:
(this document states cat6000 but is linked from the 3550 CGMP page; has both CATos and IOS CGMP/IGMP info)
also, please see this link for more 3550 IGMP troubleshooting & technotes:
if you can provide the configurations of all the devices in the MCast path, we should be able to better assist you in troubleshooting.