Where are VLAN attachments for Interconnect created and how are they scoped?

VLAN attachments are regional resources because they are directly associated with a specific Cloud Interconnect connection, which itself is provisioned in a particular Google Cloud region and physical Interconnect location. This regional scope means a VLAN attachment created in one region cannot be used to connect to a VPC network in a different region. They are not global resources that span all regions automatically; instead, separate VLAN attachments would be needed for connectivity to different regions. They are not per-project resources shared across an organization, nor are they per-VM resources; they connect a specific VPC network to an on-premises network via Cloud Interconnect.