Private subnet
A private subnet is a subnet whose resources lack direct connectivity or reachability to the public internet.
Terraform in Depth: Infrastructure as Code with Terraform and OpenTofu
A private subnet is a subnet whose resources are not directly reachable from the public internet.
- How it is used
- Places application services that should not be directly internet-accessible behind an internet-facing load balancer.
- How deep it goes
- Works through CIDR division, public-IP settings, NAT placement, and outbound routing in a Terraform subnet module.
- Examples
- Uses an API container, database, cache, and load balancer, alongside a Terraform public-and-private-subnet module.
- What you can do after
- Build it from scratch with Terraform: divide a supplied CIDR block and configure private-subnet outbound access through NAT.
Secure APIs
A private subnet is a cloud network subnet that lacks direct internet exposure and is intended for internally accessed resources.
- How it is used
- Uses network segmentation to keep internal API services away from direct internet exposure.
- How deep it goes
- Explains isolation, DMZ routing, and cross-segment bridges, but does not specify provider-specific subnet configuration steps.
- Examples
- Shows API gateways and bastion servers in a DMZ protecting private APIs, databases, and developing endpoints.
- What you can do after
- Evaluate network topology by checking internet exposure, DMZ routing, segment bridges, and restricted private access.
Related concepts
- subnetworkkind of · A subnetwork is a logical subdivision of an IP network with its own address range, routing scope, and network configuration.
- NAT gatewayuses · A NAT gateway is a network component that enables private-network resources to initiate outbound connections through address translation without accepting unsolicited inbound connections.
- network address translationuses · Network address translation is a networking technique that rewrites IP addresses and often transport-layer ports as traffic crosses a gateway or network boundary.
- network segmentationconfigured by · Network segmentation is the division of a network into distinct physical or logical zones with controlled communication between them.
- multi-tier applicationused by · A multi-tier application is an application organized into distinct tiers that separate responsibilities and interact through defined dependencies or interfaces.
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