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Public subnets contain resources that need to be accessible by the public, such as an online store’s website.

Private subnets contain resources that should be accessible only through your private network, such as a database that contains customers’ personal information and order histories.

In a VPC, subnets can communicate with each other. For example, you might have an application that involves Amazon EC2 instances in a public subnet communicating with databases that are located in a private subnet.

  • AWS reserves both the first 4 and last 1 IP addresses in each subnet’s CIDR block. In total, AWS reserves 5 IP’s for your subnet.
  • We can have only 1 IG per subnet.
  • When we create a custom VPC, no subnet or IGW is created.

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