perVLAN

perVLAN is a term used to describe configuring networking components on a per-VLAN basis. It implies that each VLAN is treated as its own logical segment with isolated broadcast domains, separate addressing, and distinct policy sets. In practice, perVLAN configurations rely on VLAN tagging, commonly using 802.1Q, to carry traffic for multiple VLANs over a single physical link. Access ports belong to a single VLAN, while trunk ports carry traffic for several VLANs with corresponding tags. PerVLAN design supports granular control of traffic, security, and quality of service.

Inter-VLAN communication requires routing, typically performed by a router or Layer 3 switch. Per-VLAN routing can be implemented via router-on-a-stick or with a multilayer switch that has SVIs (Switched Virtual Interfaces) for each VLAN. Policies such as access control lists, firewall rules, and QoS can be applied on a per-VLAN basis to constrain traffic between VLANs and to external networks. DHCP scopes, DNS settings, and other services are often configured separately for each VLAN to align with addressing and policy requirements.

Common use cases include segmenting office networks into separate VLANs for data, voice, guest, or by department, and isolating data-center tenants in a multi-tenant environment. Benefits include reduced broadcast domains, improved security, easier policy enforcement, and scalable network design. Considerations include management overhead, the need for consistent VLAN IDs across devices, proper trunk configuration, and careful planning of IP addressing and routing to avoid misconfigurations such as overlapping subnets or unintended inter-VLAN access.