Cloud Router enables you to dynamically exchange routes between your
Virtual Private Cloud (VPC) and on-premises networks by using
Border Gateway Protocol (BGP).
For example, if you use a Cloud VPN tunnel to connect your networks, you can
use Cloud Router to establish a BGP session with your
on-premises router over your Cloud VPN tunnel. Cloud Router
automatically learns new subnets in your VPC network and
announces them to your on-premises network.