VPC and Subnets CIDR Best Practices?

Hello,

There are some general guidelines you can find here: https://docs.aws.amazon.com/quickstart/latest/vpc/architecture.html

Every environment is different, you should consult with your AWS Solutions Architect for specific guidance.

Hi,

There are several approaches to consider when implementing an AWS VPC in an AWS account. In addition to this, some important things to consider are flexibility between and outside of AWS accounts.

E.g,

1/ When you consider your disaster recovery plan, you must ensure that there is no overlap or conflict with your local subnet CIDR.

2/ When you want to advertise a Virtual Private Cloud (Amazon VPC) route to your on-premises network through an AWS Direct Connect VIF BGP session, you can consider the longest/shortest VPC CIDR prefix to decide the route.

3/ VPC peering is also the point where you want to connect two Amazon VPCs

Hope it helps.

I've always used this reference document. It's a great little "Cliff Note" of VPC Design.