IPsec tunnel between AWS VPC (nat mode) <--> Fortigate (transparent mode)

[tonyo]

Hi,

I'm trying (unsuccessfully) to establish a site-to-site IPsec VPN tunnel between Amazon Web Services (AWS) Virtual Private Cloud (VPC) and a local Fortigate (FortiOS v5.2.5) in TRANSPARENT mode.

The instructions on configuring the local Fortigate assume that its in NAT mode.

I've attempted to setup the config without success.

I've setup IPsec VPNs (using fortigates) before in both NAT (only) and Transparent (only) modes.

However, this is the first time I had the need to setup a tunnel with NAT on one side and Transparent (Fortigate) on the other.

The Tunnel appears as UP (in the reported by the IPsec monitor).

I've setup (what I believe to be) the correct policies (Policy based tunnels in Transparent mode...vs Route based tunnels in NAT mode).

I'd like to take a step back and ask...

Q: Is it possible to create an IPsec tunnel between AWS VPC (in nat/route mode) and a Fortigate (in TRANSPARENT mode)?

Q: If so, are they any tricks/gotchas that I should be aware of?

Many thanks in advance.

-tony