Subnet

A deep dive into Subnet - Practical ver.

What is a Subnet?

• The IP address range of a VPC

  • It divides the VPC into segments

• AWS VPC cannot operate without subnets!

Subnet Names

• It is a conceptual division

  • public

  • private

• You don't necessarily have to use public or private as subnet names

• Separating DB subnets is a matter of preference

Subnet CIDR Block

• Subnets also require a CIDR block to be specified

• Subnet CIDRs must not conflict with each other

• Subnet CIDRs must not exceed the VPC range

  • Because the VPC size is the maximum IP constraint!

• Think of it as claiming territory within the VPC with subnets

  • If a subnet runs out of IPs, you can create another subnet in the unclaimed space!

    • However, when creating resources, there will be two subnet options, so you'll have to decide which subnet to choose...

      • Don't add subnets later -- design it properly from the start!

  • You can add subnets to the unclaimed space in the VPC, but you cannot merge two subnets