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Article Id 190975
This article describes how resolve the L4 load balance no connectivity issue on FortiADC.

'DNAT packet forwarding method' only considers destination IP address translation, keeping the source IP address in the packet.
Real servers do not reach unknown networks nor have access to list control.

The procedure consists on changing the 'packet forwarding method' from 'DNAT' to 'full NAT' by applying the following changes on device GUI:

1) To configure an IP address with the same network segment of the real server as "source pool".
Go to Load Balance -> Virtual Server -> Source Pool and configure same address as 'from' and 'to' in the range  then  save changes.

2) Go to Virtual Server, select 'VS-Name', select 'packet forwarding method' as 'full NAT' and select configured 'source pool'  then save changes .

"Full NAT" allows DNAT plus SNAT translation.