In a cloud environment (like AWS, Azure, or GCP):
- Each VPC (Virtual Private Cloud) defines a private IP address space, typically using RFC 1918 private ranges (like
10.0.0.0/16). - Within that VPC, you define subnets (
10.0.1.0/24,10.0.2.0/24, etc.). - Your microservices, running on EC2 instances, containers, or Kubernetes pods, get private IP addresses from these subnets.
-
These IPs are local to the VPC, meaning:
- Other services in the same VPC can communicate freely.
- Outside traffic cannot reach them directly.
🌐 How External Clients Talk to Microservices
To allow clients (users, frontends, external systems) to access your microservices, you need to expose them via a controlled public-facing interface.
Common Ways to Expose Microservices:
| Method | Description | Example |
|---|---|---|
| API Gateway | Fronts all your microservices with a single endpoint. Handles routing, auth, rate limiting, etc. | AWS API Gateway, Azure API Management, Kong |
| Load Balancer | Balances traffic across multiple service instances, often at Layer 4 (TCP) or Layer 7 (HTTP). | AWS ALB/ELB, NGINX, HAProxy |
| Reverse Proxy | Routes traffic from a public endpoint to internal services. | NGINX, Traefik |
| Ingress Controller | Kubernetes-specific way to expose services to the outside world. | NGINX Ingress, Istio, Ambassador |
🔁 Internal Communication
Within the VPC:
- Microservices talk to each other using private IPs or internal DNS (e.g.,
auth-service.default.svc.cluster.localin Kubernetes). - No need for public IPs or NAT.
🎯 Summary
✅ Microservices run on private IPs from subnets within your VPC
✅ They are not directly accessible from the internet
✅ You expose them using API Gateways, Load Balancers, or Proxies
✅ Internal service-to-service traffic stays within the private network
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