Networking

Simfra simulates AWS networking using Docker. Each VPC becomes a Docker bridge network, the Docker host represents the public internet, and services are either publicly accessible (ports published to the host) or VPC-only (reachable only from containers on the same network).

When SIMFRA_DOCKER=true, creating a VPC in Simfra creates a corresponding Docker bridge network. Containers launched by services like RDS, ELBv2, Lambda, and ECS are attached to their VPC's Docker network, giving them layer-3 connectivity to other containers in the same VPC - just like EC2 instances in a real AWS VPC.

How It Maps

AWS Concept Simfra Implementation
VPC Docker bridge network (simfra-vpc-{accountID}-{region}-{vpcID})
Public internet Docker host (127.0.0.1)
Internet-facing resource Container with host port published
Private resource Container on VPC network only, no host ports
VPC DNS (CIDR+2) DNS container at CIDR+2 on each VPC network
Route53 hosted zones Resolved by per-account DNS container
Service DNS names Registered automatically (ALB, RDS, ElastiCache, etc.)

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