Private networks keep backend traffic off the public internet. Use for DB, cache, and app-to-app communication. Restrict egress if needed. In multi-tenant environments, VLAN or VPC isolation is essential.
Why private networks
- Security: Backend (DB, cache, app servers) do not need to be on the public internet. Reduce attack surface and exposure.
- Performance: Private links are often lower latency and more predictable than going over the internet. No bandwidth charges for in-DC traffic in many providers.
- Compliance: Isolate sensitive data and control where traffic goes. Required or preferred for many compliance frameworks.
Use cases
- DB and cache: App servers talk to MySQL, Redis, etc. over private IPs. Only the app tier (or load balancer) needs a public IP.
- App-to-app: Microservices or internal APIs over private network. No need to expose them publicly.
- Egress control: Restrict which private instances can reach the internet (e.g. only a NAT gateway or specific hosts). Reduces data exfiltration risk.
Multi-tenant and VPC
- VLAN / VPC: In shared infrastructure, your servers are on a private VLAN or VPC so other tenants cannot reach them. Essential for security and compliance.
- Peering: If you have multiple VPCs or regions, use private peering or VPN so traffic stays off the public internet.
Summary
Use private networks for DB, cache, and app-to-app traffic. Restrict egress; in multi-tenant, ensure VLAN/VPC isolation. Reduces exposure and often cost.
