Question 1

What's the difference between a subnet and a VPC/VNet?

Accepted Answer

A VPC (AWS/GCP) or VNet (Azure) is the overall private network in the cloud. A subnet is a smaller IP range inside that network. You use subnets to separate workloads (for example, public-facing vs. internal) and to apply different routing and security rules.

Question 2

When should I use a public subnet vs. a private subnet?

Accepted Answer

Use a public subnet when resources need a direct route to the internet (commonly via an internet gateway) and may accept inbound traffic (usually through a load balancer). Use a private subnet for resources that should not be directly reachable from the internet, like databases and internal APIs. Private subnets can still reach the internet for updates via controlled egress (for example, a NAT gateway).

Question 3

How much does a subnet cost?

Accepted Answer

Creating subnets typically has no direct hourly charge in major clouds. Costs usually come from what you attach to or route through the subnet, such as NAT gateways, load balancers, VPN/Interconnect/ExpressRoute, public IP addresses, and data transfer (especially internet egress and cross-zone/region traffic).

Subnet

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