A manufacturer wants its on-premises core switches to share one extended LAN with its Google Cloud VPCs, so a legacy appliance can use a VLAN that spans both sides. The company will buy the link from a connectivity provider. Which attachment type fits?
Show answer and explanation
Answer: A
Layer 2 Partner Interconnect delivers a VLAN through a supported service provider, so the on-premises switch and Google Cloud share the same Layer 2 domain over the provider's network. The customer runs the BGP session with Cloud Router for routing. Dedicated Interconnect VLAN attachments are Layer 3, which means routing happens between them and the on-premises network. HA VPN is an IPsec tunnel that routes at Layer 3, and Cloud Router by itself is a BGP control plane rather than a connection.
Why the other options are wrong
- B. Dedicated Interconnect VLAN attachments carry Layer 3 traffic and exchange routes with BGP, so they do not extend a Layer 2 LAN between sites.
- C. HA VPN is an encrypted Layer 3 tunnel. Route-based IPsec tunnels cannot stretch a VLAN across sites, so same-subnet behavior for the legacy appliance is not provided.
- D. Cloud Router controls BGP route exchange but is not a physical or logical link. Advertising a prefix does not create a shared Layer 2 segment with on-premises switches.