VLANiin

VLANiin is a term used in computer networking to describe a method of introducing additional VLAN context by nesting VLAN tags within a frame beyond the standard single tag. In practice, it refers to carrying multiple VLAN identifiers inside a single Ethernet frame to enable hierarchical or multi-tenant separation across network devices, particularly in provider networks and data centers. There is overlap with the established concept of Q-in-Q (802.1ad), which defines VLAN stacking by adding an outer tag to an already tagged frame. Some sources use VLANiin as a descriptive alias for this approach, while others reserve VLANiin for vendor-specific or internal nomenclature.

Implementation typically involves an outer VLAN tag used by the provider or edge switch and inner VLAN tags used for customer or service-specific segmentation. This arrangement enables scalable separation without provisioning new access ports for each customer. It is important to ensure compatibility with network devices, as tag stacking increases frame size and can impact MTU, forwarding tables, and control plane processing.

Use cases include carrier Ethernet services, data center interconnect, and multi-tenant campus networks. Configurations must consider security implications such as avoiding VLAN hopping, proper isolation between tenants, and consistent tagging policies. Management considerations include visibility into nested tags, traceroute behavior, and compatibility with monitoring tools.

VLANiin is not universally standardized as a separate protocol; it is commonly realized via Q-in-Q or vendor-specific tagging schemes. For formal reference, one should consult 802.1Q and 802.1ad specifications and vendor documentation for exact capabilities and limitations.