Select the VPC where you plan to provision the Network Load Balancer.
Under Mappings, select Availability Zones and the corresponding subnet for each.
For IPv4 settings, IPv4 address is selected by default. Select Use an Elastic IP address from the dropdown list to assign to your Network Load Balancer.
After you specify the Elastic IP address for the Network Load Balancer, complete the remaining steps for creating a Network Load Balancer. Note: After a Network Load Balance is created, you can't change its subnets and Elastic IP addresses. However, you can use subnets for other Availability Zones to deploy additional NLB nodes with either AWS-assigned or Elastic IP addresses.
Add a new node with an Elastic IP address to an existing Network Load Balancer
Choose the Region where your Network Load Balancer is located.
Under Load Balancing, choose Load Balancers.
Select your Network Load Balancer.
Choose Actions, and then choose Edit Subnets.
Select a subnet from the remaining Availability Zones.
For IPv4 address, select Choose an Elastic IP. A dropdown list appears, containing each of the Elastic IP addresses in the specified Region. Note: If the Choose an Elastic IP option is unavailable, then you must allocate an Elastic IP address for the Network Load Balancer elastic network interfaces.
Choose Save. A new Network Load Balancer node is created in the subnet that you specified.
(Optional) Confirm that you've correctly configured your Elastic IP address attachments