...

 To avoid confusion before the instance can be restarted, the new interface can be renamed to its final name using the command 
     ip link set eth0 name ensY && ip link set ensY up

Address Assignement Information

Each VPC is assigned a block of private IP addresses. This block can be split by the user to form several IP subnets. Routing between such subnets is automatically enabled.

When an E2C instance is launched into the default VPC and a public subnet, the default behavior is as follows:

• If the instance has only one network interface, it is automatically assigned a private IP address from the address range assigned to the public subnet and a public IP address. This network interface is the primary network interface. It is called eth0 on the AWS level (please refer to the interface naming section to learn about the interface names presented to the operating system).
• If the instance has more than one network interface, it is automatically assigned a private IP address for each of the network interfaces - but no public IP address.

The default behavior can be modified, for example:

• Manually assigning a private IP address from the subnet range.
• Enabling or disabling the automatic assignment of a private IP address to deviate from the subnet setting.
• Manually assigning a public IP address from the AWS range or the customer range.

Public IP addresses are not directly visible to the instance. The instance operating system always works with the private address. For external connections, the private address is mapped to the public IP address via NAT.

Reserved addresses (important, if manual address assignment is used):

The following address range is reserved to allow AWS to query meta-data about instance configuration: 169.254.0.0/16. This range is automatically configured on every network interface.

The following addresses are reserved in each subnet and cannot be used for E2C instances (shown in the example below for network 10.1.1.0/24):

• 10.1.1.0: the network address
• 10.1.1.1: reserved by AWS for the VPC router
• 10.1.1.2: reserved by AWS in any subnet; the second host address in the base VPC network range is the DNS server for the VPC.
• 10.1.1.3: reserved by AWS for future use
• 10.1.1.255: network broadcast address; AWS networks do not use broadcasts.

An automatically assigned public IP address is released (and not re-assigned) by AWS for example if

• a second interface is added to the instance and the instance is then stopped and restarted,
• an Elastic IP is associated with the the instance,
• an Elastic IP address is associated with the primary interface of the instance.

See https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/using-instance-addressing.html for details.

An automatically assigned public IP address is not persistent. Every time a instance starts, it is assigned a new public IP address. If persistent public addresses are needed, use Elastic IP addresses.