How do I change the subnet mask for the default subnet of my default Amazon VPC?

Last updated: 2019-04-25

I want to change the subnet mask for the default subnet of my default virtual private cloud (VPC) in Amazon VPC. How do I change it?

Short Description

You can delete the default subnet for your default VPC and replace it with customized configurations.

Resolution

  1. Delete the default subnet for your default VPC in an AWS Region. 
  2. Create a new subnet with your preferred subnet mask size. Be sure that the new subnet is part of your default VPC in the same AWS Region.
    Note: The first four IP addresses and the last IP address in each subnet CIDR block aren't available for your use. These IP addresses can't be assigned to an instance. 
  3. Open a case with AWS Support to designate the new subnet as the default subnet for your default VPC. Be sure to provide your AWS account ID, the AWS Region, and the subnet ID.
    Note: Default subnets can only be designated for a default VPC. Make sure that the new subnet you create is part of your default VPC in that region. 

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