I'd like to know one thing about 4500 switches. Why are part numbers for main and redundant supervisors different? I mean, why two different PNs exist: ws-x4516 and ws-x4516/2? Is it a means of tracking something or the modules are indeed different?
What if I have a 4507R and two ws-x4516 and no ws-x4516/2? Can I build a redundant system and get RPR to work?
To add to Reza's comments, the existence of the two Part IDs doesn't extend beyond the ordering tools/price lists.
If you order a WS-X4516/2 and insert it in a chassis, the output of show mod will display as WS-X4516.
IIRC, the difference in the part IDs exists for the purposes of pricing bundles, but serves no purpose in terms of system operation.