4.1 Virtual networks and subnets

The same thing, three names

One idea, sold under a different brand by each provider. Learn it once and you can read any job advertisement.

On AWS

VPC

On Azure

Virtual Network (VNet)

On Google Cloud

VPC Network

Work through these

• Virtual network, CIDR planning and subnetting

  Your own private network in the provider's data centre, with an address range you choose and divide up. Planning this well is what makes everything later in the module possible.

• Public vs private subnets; route tables and internet gateways

  A subnet with a route to the internet is public and one without is private, and putting the database in the second kind is the core defensive move. The route table is what actually decides which is which.

• NAT for outbound-only access

  Machines in a private subnet often still need to reach out for updates without being reachable themselves, and a network address translation gateway is how that one-way path is built.

• Planning address space you will not run out of

  Address ranges are painful to change once systems are running, so this item is about leaving room now. Running out later means renumbering or bolting on ranges that do not fit.