I just want to make sure if I understood correctly.
AWS VPC doesn’t support transitive VPC peering (or rather – transitive routing). Then how Transitive VPC is implemented? I had searched a little and I found that the Transitive VPC needs to run a 3rd party routering controller effectively implementing the transitive routing on top of AWS networks. Did I understand it correctly?
Hi Gabriele. I would recommend to take a look at AWS Transit Gateway (https://aws.amazon.com/transit-gateway/). It will allow you to attach both VPNs and VPCs. Through AWS Resource Manager (https://aws.amazon.com/ram/) you can share resources like the Transit Gateway with other accounts or in the same account. SImilar to VPC peering you will have to accept the share. After you have attached all VPCs to the Transit Gateway in a Hub and Spoke manner you can route to all VPCs. Hope this helps.
here is about transit VPC https://docs.aws.amazon.com/en_us/solutions/latest/cisco-based-transit-vpc/architecture.html
It uses Cisco csr instance in transitive VPC to make hub-and-spoke connection through it to other VPCs or on-prem.
Take a note, that it uses VPN, not peering. Transitive piring is impossible.