I have an app running in a VPC, with (currently) a VPN connection to the development location. The app is accessible at, let's say, 10.0.2.25 (IP of the internal ELB, accessible only via VPN). The VPN-capable router I have (aka. client gateway) has no BGP capabilities.
The CIDR of the network I'm on (client network is 192.168.1.0/24) and on the VPC there is a Virtual Private Gateway (vgwA) and a corresponding routing rule (Destination 192.168.1.0/24; Target wgwA).
I can access the app without any problem (all ACL/Security Groups are properly configured).
My question is what happens when I want to create another VPN connection to a different site, but whose network has the same CIDR block (192.168.1.0/24) or a CIDR block that might overlap (or include) it (e.g. 192.168.1.0/16)? Is this successful - and will the users on the client networks be able to access the app?
Basically, what do I need to be capable to make VPN connections to different networks which have the same (or partially common) CIDR? BGP-capable customer gateway? Different virtual gateways on the same VPC? (I don't think that AWS allows that - and it doesn't really make sense) Routing rules based on the external IP of the customer gateway? (e.g. Destination: 126.96.36.199 Target: vgwA; - doesn't really make sense)