Cloud Router uses Border Gateway Protocol (BGP) to exchange routes between your Virtual Private Cloud (VPC) network and a remote network. On Cloud Router, you configure an interface and a BGP peer for your on-premises router. The interface and BGP peer configuration together form a BGP session.

Within Google Cloud, a Cloud Router interface connects to exactly one of the following Google Cloud resources:

• A Classic VPN tunnel using dynamic routing
• An HA VPN tunnel (using dynamic routing as required)
• A VLAN attachment for Cloud Interconnect
• A Router appliance instance using Network Connectivity Center

A Cloud Router supports multiple interfaces. You don’t need to create a separate Cloud Router for each Cloud VPN tunnel or VLAN attachment. However, each Cloud Router uses the same ASN for all its BGP sessions. Because Partner Interconnect requires a public ASN, and all other types of interface require private ASNs, a Cloud Router that manages BGP sessions for a VLAN attachment on Partner Interconnect cannot manage BGP sessions for any other type of interface.