I'm having some kind of discussion with a consultant in the agency i provide IT services. He says that in a network that have layer 2 and layer 3 switches, it could cause collision and broadcast problems. In all years of experience i have in this area, including the CCNA, there's no way this issue happens. Of course, every port creates a collision domain, but in switching it only happens exclusively in every port for themselves. And all of the network i've been lately, their networks are configured this way, layer 2 switches for network components like PC, printers, ect... and layer 3 switches for Vlan's and routing, including interconnect segments in the network, so it seems that this guy says that all my network switches, should be layer 3, that cost a lot of money or use layer 2 switches and use routers to connect segments, and router are really slow making this decision, compared to a switch layer 3. I just want to know if this theory or fact, is possible or is viable. Please, if anybody can reply, the better, because this i have to present it as evidence to the administration, because i haven't found anything on the web agreeing with this theory or fact of his.