VIP type of Forwarding (IP) with fast layer 4 profile

This article explains it:

https://support.f5.com/csp/article/K7595

An IP forwarding virtual server accepts traffic that matches the virtual server address and forwards it to the destination IP address that is specified in the request rather than load balancing the traffic to a pool. Address translation is disabled when you create an IP forwarding virtual server, leaving the destination address in the packet unchanged. When creating an IP forwarding virtual server, as with all virtual servers, you can create either a host IP forwarding virtual server, which forwards traffic for a single host address, or a network IP forwarding virtual server, which forwards traffic for a subnet.

IP Forwarding Virtual Servers act more like routers than a typical virtual server. They forward requests to the destination specified in the request, as opposed to sending the traffic to a pool member.

See also this post:

https://devcentral.f5.com/questions/usage-cases-for-forwarding-ip-virtual-server-forwarding-layer-2-virtual-server-53124