When using a LoadBalancer as a Service type in kubernetes, it starts off by creating a NodePort service in the background to facilitate communication, the control plane will allocate the port from a default range port: 30000-32767. Then, configures the external load balancer to forward traffic to the assigned service port by cloud-controller-manager.

If you want to toggle this type of allocation you may set the field as:

spec: 
  allocateLoadBalancerNodePorts: #true or false