The Gateway Load Balancer, or GLB, is the final load balancing option in AWS. It operates on layer 3 and it has a very important function. You use the GLB to forward traffic to other network devices, such as firewalls, IPS, IDS, etc. The traffic enters the load balancer, goes to the appropriate target groups containing your EC2 instances running 3rd party security appliance or private IPs of physical network appliances and those forward it back to the load balancer once the traffic has been analyzed which distributes the traffic to the instances. It operates on GENEVE protocol on port 6081.