Breaking up a big part of network in to smaller network called as "Network Segmentation", Why do you need to break your networks? Because of the "LAN congestion", Such as
- Broadcast storms
- Low Bandwidth
- Adding hubs for connectivity
- A bunch of ARP (Address resolution Protocol) or IPX (Novell)
- Too many hosts in a broadcast domain.
Routers, Switches, and bridges do "Network Segment" except Hub also known as "Multi repeater",