jpasset

I do know of some multicast issues between the 8600 and the 5500 series switches. We have a issue with multicasting at one of our customers. This is especially prevalent when split-multilink trunking is operational between the two types of switches.
Nortel is currently working on a maintenance release for us. Can let you know when it is released (+- mid July).
In the meantime, If you are using S-MLT uplinks to the 8600 and depending on what you are using multicasting for, and how you are using it, it may help to disable IGMP-Snooping on the 5520.

1fastmf

What type of modules are you running on your ERS8600? Standard, E, M, or R? What version of code are you running, and what model CPU/Switch Fabric do you have? (8690, 8691, 8692). There are definately known limitations with some instances of multicast and SMLT. I believe one work around is using DVMRP instead of PIM in some routed scenarios. What does the L2 and L3 topology look like?

With 4.x code and R modules, with ERS55xx switches at the edge, there is currently several working and supported configs. If you give me more detail I might be able to help. Had the same situation over 6 months ago with a client trying to get real time displays for the Agent Desktop Display. Are you using Unicast as a work around, or are you specifically stuck with ADD and not supervisors?