Virtual Private Clouds

Cloud resources need to communicate without exposing every machine directly to the public Internet. A virtual private cloud, or VPC, supplies an isolated logical network inside a public cloud.

What the VPC Owns

A VPC typically defines:

• address ranges assigned to connected resources;
• subnets that divide the address space;
• routes that decide where packets go;
• firewall rules that permit or reject traffic; and
• connections to the Internet, other VPCs, or external networks.

The cloud provider implements these controls on shared physical infrastructure. “Private” describes the logical network boundary; it does not mean the application runs in a personally owned data center.

Subnets and Routes

A subnet groups addresses within part of the network. Routes then decide whether traffic stays inside the VPC, crosses to another subnet, reaches an attached network, or uses an Internet gateway.

The provider may manage the underlying virtual routers, but the customer still owns the intended topology. A route can make a destination reachable; it does not by itself authorize the traffic.

Reachability and Permission Are Separate

A useful debugging sequence is:

1. Does DNS resolve the intended destination?
2. Is there a valid route to its address?
3. Do firewall rules allow the protocol and direction?
4. Is the service listening and healthy?
5. Does application-level identity permit the operation?

Network reachability and IAM answer different questions. A firewall may allow packets to arrive while IAM rejects the requested operation.

Connecting Network Boundaries

Separate VPCs can be connected through peering or a shared network arrangement. External networks can connect over an encrypted tunnel on the Internet or through dedicated provider connectivity.

Every connection expands the reachable network. Add it with explicit routes, traffic policy, ownership, and failure behavior rather than treating connectivity as proof of trust.