Interconnect Attachment (VLAN)

An Interconnect attachment is the VLAN that carries traffic from a Dedicated or Partner Interconnect into a specific VPC, billed a fixed hourly rate by capacity. Attachments outlive the projects they served surprisingly often.

Provisioned capacity is the meter, not the packets

Each attachment bills a fixed hourly rate determined by the capacity it was provisioned with, and the meter is indifferent to throughput: an attachment sized generously and used lightly pays exactly what a saturated one does. This is the same billed-on-provisioned-not-consumed shape as a persistent disk, applied to network capacity. Because attachments are configured once and then forgotten, the mismatch between provisioned size and actual need tends to persist for years rather than weeks.

One physical port, many billed VLANs

The parent Interconnect is the physical circuit; attachments are how that circuit fans out. Every VPC that needs the on-premises path gets its own VLAN attachment, and every one of those attachments is a separate hourly charge. Fan-out is where the spend multiplies quietly: adding a project to the hybrid network feels free at the time, but each addition is a new fixed meter that will need its own decommissioning later.

Attachment rows in ZopNight’s inventory

ZopDev discovers attachments through Cloud Asset Inventory and attributes their fixed hourly charges from billing actuals, tying each VLAN to its parent circuit and its VPC in topology. Attachments cannot be scheduled, because capacity is either provisioned or deleted with nothing to pause between. The platform’s contribution is therefore making sure every attachment’s charge lands against a named project instead of dissolving into a general networking line.

VLANs that survived their projects

The waste patterns here are all about outliving purpose: an attachment into a VPC whose environment was decommissioned, still holding capacity for traffic that stopped months ago; duplicate attachments created during a re-architecture with the old path never removed; and oversized capacity chosen “to be safe” for a workload whose real transfer needs turned out to be a fraction of it.

Inspecting attachments from the Interconnect page

Google Cloud console → Network Connectivity → Interconnect → VLAN attachments lists every attachment with its capacity, region, parent connection, and target VPC. That is the list to reconcile against the projects that still exist.