The IDs of the public subnets. You can specify only one subnet per
Availability Zone. You must specify either subnets or subnet mappings.
[Application Load Balancers] You must specify subnets from at least
two Availability Zones. You cannot specify Elastic IP addresses for your
subnets.
[Application Load Balancers on Outposts] You must specify one Outpost
subnet.
[Application Load Balancers on Local Zones] You can specify subnets
from one or more Local Zones.
[Network Load Balancers] You can specify subnets from one or more
Availability Zones. You can specify one Elastic IP address per subnet if
you need static IP addresses for your internet-facing load balancer. For
internal load balancers, you can specify one private IP address per
subnet from the IPv4 range of the subnet. For internet-facing load
balancer, you can specify one IPv6 address per subnet.