FSX - IP allocation

When you create a DataSync task to read from FSx or write to FSx, DataSync will create 4 ENIs in the VPC and Subnet where your primary FSx server is located. Each ENI consumes one IP address from the Subnet IP range. These ENIs persist until the DataSync task is deleted. For more information, see https://docs.aws.amazon.com/datasync/latest/userguide/datasync-in-vpc.html.

Hello,

By definition, FSx would get one or two ENIs assigned with one IP each depending on the deployment (single AZ or multi AZ). The IP allocation per se happens when you create a Subnet within a VPC and assigned a IP CDIR range (see references 1 - 3).

I hope this helps, please do feel free yo share the steps you are following if necessary.

1. Obtaining the correct file system IP addresses to use for DNS - https://docs.aws.amazon.com/fsx/latest/WindowsGuide/file-system-ip-addresses-for-dns.html
2. VPCs and subnets - Subnet basics - https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html#subnet-basics
3. Work with VPCs and subnets - Create a subnet in your VPC - https://docs.aws.amazon.com/vpc/latest/userguide/working-with-vpcs.html#AddaSubnet