Is subnetting still relevant?
The main purpose of subnetting is to help relieve network congestion. Congestion used to be a bigger problem than it is today because it was more common for networks to use hubs than switches. When nodes on a network are connected through a hub, the entire network acts as a single collision domain. What this means is that if one PC sends a packet to another PC, every PC on the entire network sees the packet. Each machine looks at the packet header, but ignores the packet if it isn’t the intended recipient. The problem with this type of network is that if any two machines on the network happen to send packets simultaneously, then the packets collide and are destroyed in the collision. The two machines then wait a random amount of time and resend the packets. The point is that an occasional collision is no big deal, but excessive collisions can slow a network way down. Switches solve the excessive collision problem by directing packets directly from the source machine to the destination
