Refer to the exhibits.

The exhibits identify a source at 10.0.1.101 generating an ICMP echo toward a public destination. They show multiple Internet-facing SD-WAN members, but not a session-table record or packet capture tying this exact ICMP exchange to port2. The corporate service requires a private destination, so it is not the controlling match for the Facebook public IP address. Application classification must also be distinguished from a basic ICMP ping: a Facebook application signature associated with HTTPS traffic does not establish that an ICMP exchange has been recognized as the Facebook application. Although D (port2) is the supplied key, the displayed service definition and application-cache information alone do not prove it. To determine the correct egress, capture the specific ICMP flow or apply a source/destination session filter and inspect the selected SD-WAN member and outgoing device. Port1, port2, and port4 remain potential candidates until the relevant interface and route-selection evidence is supplied. Accordingly this is not an exhibit-verified single-answer item, and it should not be sold as conclusively solved solely from the provided screenshot. The FortiOS Application Steering guide documents why application detection and rule eligibility must be examined separately.

Verification qualification: The available exhibits do not uniquely prove port2 as the ICMP egress interface.