What technology is used to aggregate multiple physical networks into a single logical network?

The technology that aggregates multiple physical networks into a single logical network is VLAN (Virtual Local Area Network). VLANs allow network administrators to segment a single physical network into multiple logical networks, which can operate independently and have different network policies. This is especially useful in large organizations where different departments may need their own network configuration while sharing the same underlying physical infrastructure.

By employing VLANs, you can isolate traffic for security purposes, improve network efficiency, and simplify management by grouping users or devices based on functionality, regardless of their physical location. VLANs use tags in Ethernet frames to differentiate between the various logical networks, making communication across the same cable infrastructure possible without requiring additional physical hardware.

Subnetting, while related to creating logical network segments, refers specifically to dividing an IP address space into smaller, manageable segments rather than physically grouping distinct networks. A VPN (Virtual Private Network) serves to secure connections over public networks but does not aggregate networks in the way VLANs do. Routing directs data packets between different networks but does not, by itself, create logical networks from physical networks.