AWS Network Architecture (VPC)

Overview

This document describes the network topology for the cloud infrastructure. The design follows the principle of Network Segmentation to isolate public-facing services from internal applications and databases.

• Region: eu-central-1 (Frankfurt)
• VPC Name: main-production-vpc
• Total CIDR: 10.200.0.0/20
• Total Available IPs: 4.096

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Subnet Plan (Availability Zone A)

Tiered Subnet Design:

Subnet Name	CIDR Block	IP Range	Hosts (Total)	Zweck
Private Subnet A	10.200.0.0/21	10.200.0.0 - 10.200.7.255	2.048	Application Layer. Applications (EC2, EKS Nodes). no internet access (only via NAT). max. size for scaling.
Public Subnet A	10.200.8.0/24	10.200.8.0 - 10.200.8.255	256	Ingress Layer. Load Balancer, Bastion Hosts or NAT gateways. Internet access via IGW.
Data Subnet A	10.200.9.0/24	10.200.9.0 - 10.200.9.255	256	Persistence Layer. DBs (RDS), Redis. Isolated. No internet access.
Reserved	10.200.10.0/23+	...	~1.500	Reserved for future expansion or AZ B.

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Architecture Logic (Mini-ADR)

Decision: Subnet Sizing

We assigned a /21 block (50% of the total VPC) to the Private Subnet.

• Reason: Future-proofing for AWS EKS.
• Public/Data: A /24 is sufficient for Ingress and databases at this scale.

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Visual Topology (Mermaid)

graph TD
    %% Globale Elemente
    Internet((Internet))
    IGW["Internet Gateway (IGW)"]

    %% VPC Definition
    subgraph VPC ["VPC: 10.200.0.0/20"]
        direction TB

        %% Availability Zone A
        subgraph AZA ["AZ A (eu-central-1a)"]
            direction TB
            PubA["Public Subnet A (/24)<br>10.200.8.0"]
            PrivA["Private Subnet A (/21)<br>10.200.0.0 - 7.255<br>Core Workloads"]
            DataA["Data Subnet A (/24)<br>10.200.9.0<br>RDS / DBs"]
        end
    end

    %% Verbindungen
    Internet --> IGW
    IGW <--> PubA
    PubA -- "Traffic Routing" --> PrivA
    PrivA -- "Database Connections" --> DataA

    %% Styling passend zum Slate Theme
    classDef public fill:#1e88e5,stroke:#0d47a1,stroke-width:2px,color:#fff;
    classDef private fill:#43a047,stroke:#1b5e20,stroke-width:2px,color:#fff;
    classDef data fill:#e53935,stroke:#b71c1c,stroke-width:2px,color:#fff;

    class PubA public;
    class PrivA private;
    class DataA data;