Refer to the exhibit.

The correct answer is D. You can configure forward domain IDs for each network .

The study guide explains that in FortiGate transparent mode, all interfaces belong to the same broadcast domain, even interfaces with different VLAN IDs , and then states that you can “subdivide into multiple broadcast domains” by configuring set forward-domain < domain_ID > . It also states that “interfaces with the same domain ID belong to the same broadcast domain” and, with multiple forward domains, “traffic arriving on one interface is broadcast only to interfaces in the same forward domain ID.” That is the mechanism used to separate internal networks and confine traffic between network segments.

The other options do not fit this requirement. Universal ZTNA is for application access control, not segmentation between two OT networks. One traffic VDOM does not create segmentation by itself; multiple VDOMs would be needed for that type of isolation. An explicit software switch controls intraswitch traffic inside the same software-switch domain, not segmentation between separate networks like network 1 and network 2. Therefore, the correct way to implement the internal segmentation asked in the question is to assign different forward domain IDs to each network.