We just recently tried this and it does NOT work.  The reason is that the vMX (and any MX for that matter) will not route from a Meraki Auto-VPN connection to a 3rd party site to site connection.  So you can stand it up, but you can't route traffic from the branch MX to the AWS VPC connected by the AWS VPN.  We have modified our architecture so that we have a site-to-site VPN from every branch MX to the other AWS VPCs that we need to access.  Not the best, but the only option. ... View more

We have not tried this yet, but we did try to connect a branch MX back through a vMX to a peered VPC and that did not work.  So, our case looked like this:   MX ><AUTOVPN><vMX/VPC-A><VPC PEERING><VPC-B   I can ping VPC-B from the vMX and vice versa, but when I ping from the MX to VPC-B, I get no return traffic.  With doing a packet capture, I can see the ping hit the vMX and be sent to VPC-B, but I never get return traffic to the vMX that would be passed to the MX.  Essentially, the VPC peering does not allow routing across the peering connection.   We are getting ready to try exactly what you are proposing.  Let me know how it goes for you! ... View more

There is actually communication allowed between VPCs.  See https://docs.aws.amazon.com/AmazonVPC/latest/PeeringGuide/Welcome.html.  I'm just wondering whether I can use this type of peering to send traffic from all VPCs destined to the branch network across the Auto-VPN/SDWAN to flow through the one vMX.  It sounds as if that is not the case though, which means this client will have to have a vMX for each VPC.  Bummer! ... View more

Did you ever get this figured out?  I have a client with 3 VPCs, all in the same AWS account, and I'm wondering if I install a single vMX in one of the VPCs, if I can connect other subnets in the other 2 VPCs back through the SDWAN of the single vMX via VPC Peering.   Has anybody done this? ... View more