Network segmentation is the practice of dividing a network into smaller, isolated segments separated by boundaries such as VLANs and firewalls. This containment means problems in one segment don’t automatically affect others, and you can control who can move between segments. Security-wise, segmentation limits the blast radius and greatly reduces lateral movement. If malware or an attacker breaches one segment, they’re much less able to reach critical systems in other segments. Policy enforcement becomes clearer and stronger because you can apply access controls at the segment boundaries, using VLANs to separate broadcast domains and ACLs or firewalls to filter traffic between segments. On the performance side, smaller broadcast domains mean fewer devices see each broadcast, reducing unnecessary traffic and helping with congestion. It also makes it easier to apply quality of service and troubleshoot issues because traffic is more predictable and localized. In practice, this is achieved by using VLANs to create distinct network sections and ACLs (often in combination with firewalls) to enforce who can access each segment. That combination—segment boundaries plus targeted policy—delivers the security and performance benefits described.