Limiting Discovering

I am trying to discover the network infrastructure only, i get too many items when i do scans. I have tried only scanning router, switches only and other combinations. I am trying to ONLY discover Switches, Routers, Wireless AP.. anyone able to tell me how to do that?

this could be very inaccurate. how would one tell a linux workstation from a linux router? or a windows server from a windows gaming machine …