Source Interface NAT
(2015-03-10)
If traffic is going from trust to the vpn zone, and that traffic matches the rule supplied, then NAT the outbound traffic to the interface's IP.
set security nat source rule-set example-nat from zone trust
set security nat source rule-set example-nat to zone vpn
set security nat source rule-set example-nat rule example-nat-rule match source-address 172.16.0.0/16
set security nat source rule-set example-nat rule example-nat-rule match destination-address 192.168.200.0/24
set security nat source rule-set example-nat rule example-nat-rule then source-nat interface