A Gateway Load Balancer (GWLB) is a service that makes it easy to deploy, scale, and manage virtual appliances, such as firewalls and intrusion detection systems, by combining a transparent network gateway (Layer 3) with a load balancer (Layer 4) [citation:1][citation:6].
A Gateway Load Balancer (GWLB) is designed to deploy, scale, and manage fleets of third-party virtual appliances, such as firewalls, intrusion detection and prevention systems (IDS/IPS), and deep packet inspection (DPI) systems [citation:1]. It operates at Layer 3 (the network layer) by acting as a transparent network gateway for all traffic. It combines this with a Layer 4 load balancer to distribute traffic to the appliance fleet and then routes the traffic back to its original destination [citation:6].