transparent mode

Good day all,

we have issues with some traffic with fortigates. below is the general direction of traffic, ip's used below are random.

this source destination sits between a fortigate (version6.0) that has both nat and transparent mode.

this traffic can be seen reaching transparent mode firewall but there is not return ack being seen after that.

source is 192.168.100.11 & destination is 201.111.152.7 on port 443

192.168.100.11 - nat mode - transparent mode - 201.111.152.7

appreciate all help with this problem.