I set up a hub VPC with 2 CRs. One for interconnects, and another for HA VPNs to connect to spoke VPCs. All CRs are set to advertise all subnets and learned routes. What do I need to allow end to end advertising of on prem prefixes learned over BGP? For eg: 10.0.0.0/24 is learned by Hub CR router that connects to the interconnect. The other Hub CR router that is used for HA VPN to other spoke VPCs should advertise the 10.0.0.0/24 down to the spoke VPC CRs. Do I need to add custom advertised subnet all along the way? I was hoping BGP dynamic propagation would take care of it. I'm not learning the routes in spoke VPCs.
Do I need to add a custom advertised subnet all along the way?
Yes, you need to have a connection between them all the way.
This is some of the information I was able to find regarding dynamic routing:
Each VPC network has an associated dynamic routing mode that controls the behavior of all of its Cloud Routers. Cloud Routers manage BGP sessions for Google Cloud connectivity products.
For a description of dynamic routing mode options, see Effects of dynamic routing mode in the Cloud Router documentation.
The following IP addresses are advertised within a VPC network:
If you connect VPC networks using VPC Network Peering, subnet ranges using private IPv4 addresses are always exchanged. You can control whether subnet ranges using privately used public IPv4 addresses are exchanged. Global internal IPv4 addresses are never exchanged using peering. For additional details, see the VPC Network Peering documentation.
When you connect a VPC network to another network, such as an on-premises network, using a Google Cloud connectivity product like Cloud VPN, Cloud Interconnect, or Router appliance:
Here is more detailed information about Dynamic routing mode and a working example that can be helpful.