A hardware load balancer is a proprietary appliance built on custom ASICs to load balance network traffic.
Why you should consider replacing your hardware load balancer with software?
Avi Networks typically refers to hardware load balancers as legacy ADCs because they are managed as individual appliances, not as service instances. Some appliance vendors provide a manager of managers for device management, but the pitfalls of element/device management versus SDN are well known. A true SDN architecture is needed to provide services for the cloud.