Cisco Systems' Private VLANs: Scalable Security in a Multi-Client Environment

This document describes a mechanism to achieve device isolation through the application of special Layer 2 forwarding constraints. Such a mechanism allows end devices to share the same IP subnet while being Layer 2 isolated, which in turn allows network designers to employ larger subnets and so reduce the address management overhead. Some of the numerous deployment scenarios of the aforementioned mechanism (which range from data center designs to Ethernet-to-thehome-basement networks) are mentioned in the following text to exemplify the mechanism’s possible usages; however, this document is not intended to cover all such deployment scenarios nor delve into their details.