VLANinterface

A VLANInterface is a logical network interface that represents a single virtual local area network (VLAN) on a device. It provides a Layer 3 addressing point for that VLAN, allowing IP-based communication, routing, and network services to be associated with the VLAN. VLAN interfaces are commonly used on routers or Layer 3 switches to enable inter-VLAN routing, and they can also be created on hosts to connect a device to a specific VLAN.

The VLANInterface operates over an 802.1Q tagged trunk. A trunk port carries traffic for multiple VLANs, with each packet tagged by its VLAN identifier (VID). The VLANInterface is configured with an IP address and serves as the gateway for devices in that VLAN. For routing between VLANs, a device hosting multiple VLANInterfaces must perform inter-VLAN routing, typically enabled by routing software or hardware.

Support and implementation vary by platform. In Linux, VLANInterfaces are implemented as subinterfaces, for example eth0.10 or a dedicated vlan.10, created with commands that define the VLAN ID and assign an IP address. On Cisco devices, a typical approach is to configure a switched virtual interface (SVI) such as interface Vlan10 with an IP address and enable IP routing on the device; the SVI acts as the gateway for the VLAN. Other vendors provide similar constructs under different names but with the same basic concept: a logical interface tied to a VLAN ID rather than a physical port.

Key considerations include ensuring the trunk allows the VLAN, assigning appropriate IP addresses and gateways, and recognizing that the VLANInterface is a software abstraction atop a physical link, subject to MTU, ARP behavior, and security policies.