VPC Showdown: AWS vs GCP Network Architecture Deep Dive

Virtual Private Clouds (VPCs) are the foundation of cloud networking, but AWS and GCP take fundamentally different approaches. Understanding these differences is crucial for architects designing multi-cloud solutions or migrating between platforms.

The Fundamental Philosophy Difference

This isn't just semantics—it impacts everything from disaster recovery to cost optimization.

Subnet Architecture: The Core Divergence

AWS Approach: AZ-Bound Subnets

VPC: 10.0.0.0/16 (us-east-1)
├── Subnet-1a: 10.0.1.0/24 (us-east-1a)
├── Subnet-1b: 10.0.2.0/24 (us-east-1b)
└── Subnet-1c: 10.0.3.0/24 (us-east-1c)

• • High availability requires duplicating subnets across AZs
• • More complex CIDR planning
• • Explicit control over resource placement
• • Network ACLs at subnet level

GCP Approach: Regional Subnets

VPC: my-vpc (Global)
├── Subnet-us: 10.0.0.0/20 (us-central1)
├── Subnet-eu: 10.1.0.0/20 (europe-west1)
└── Subnet-asia: 10.2.0.0/20 (asia-east1)

• • Automatic multi-zone high availability
• • Simpler CIDR management
• • Less granular control
• • Resources automatically distributed across zones

Routing: Implicit vs Explicit

AWS Routing Tables

# AWS Terraform Example
resource "aws_route_table" "private" {
  vpc_id = aws_vpc.main.id

  route {
    cidr_block     = "0.0.0.0/0"
    nat_gateway_id = aws_nat_gateway.main.id
  }
}

resource "aws_route_table_association" "private" {
  subnet_id      = aws_subnet.private.id
  route_table_id = aws_route_table.private.id
}

Every packet follows explicit routes. No route = no connectivity.

GCP Implicit Routing

# GCP Terraform Example
resource "google_compute_network" "vpc" {
  name                    = "my-vpc"
  auto_create_subnetworks = false
  # Routes are automatically created for subnets!
}

resource "google_compute_subnetwork" "subnet" {
  name          = "my-subnet"
  network       = google_compute_network.vpc.id
  ip_cidr_range = "10.0.0.0/20"
  region        = "us-central1"
  # No explicit route needed for internal communication
}

GCP's approach is simpler but can be "too magical" for complex scenarios.

Security Models: Groups vs Rules

AWS: Security Groups + NACLs

{
  "IpProtocol": "tcp",
  "FromPort": 443,
  "ToPort": 443,
  "IpRanges": [{"CidrIp": "0.0.0.0/0"}]
}

{
  "RuleNumber": 100,
  "Protocol": "6",
  "RuleAction": "ALLOW",
  "CidrBlock": "10.0.0.0/16",
  "PortRange": {"From": 443, "To": 443}
}

GCP: Firewall Rules with Tags

# GCP Firewall Rule
priority: 1000
direction: INGRESS
sourceRanges: ["0.0.0.0/0"]
targetTags: ["web-server"]
allowed:
  - IPProtocol: tcp
    ports: ["443"]

VPC Peering: Different Philosophies

AWS VPC Peering

• • Non-transitive (A→B and B→C doesn't mean A→C)
• • Regional (cross-region supported but separate connection)
• • Requires route table updates on both sides
• • No overlapping CIDR blocks allowed

GCP VPC Peering

• • Also non-transitive
• • Global by default
• • Routes automatically exchanged
• • Overlapping subnets allowed (with restrictions)
• • Can export/import specific subnet routes

Private Google/AWS Access

AWS PrivateLink & VPC Endpoints

• • Creates ENI in your subnet
• • Uses private IP from your CIDR
• • Costs: ~$0.01/hour + data transfer Gateway Endpoints (S3 & DynamoDB):
• • Free
• • Route table entry
• • Regional only

GCP Private Google Access

# Enable for a subnet
gcloud compute networks subnets update my-subnet \
  --enable-private-ip-google-access

• • No additional IP addresses needed
• • Works globally
• • Free (no endpoint charges)
• • Covers all Google APIs and services

Inter-region Connectivity

AWS: You Build It

1. VPC Peering (per connection cost)
2. Transit Gateway ($0.05/hour + data)
3. VPN connections
4. Direct Connect

GCP: Built-In Global Network

• • Single VPC spans all regions
• • Internal IPs communicate globally
• • Premium network tier uses Google's backbone
• • Costs only for egress traffic

Cost Implications

AWS Hidden Costs

• • NAT Gateway: $0.045/hour +$0.045/GB
• • VPC Endpoints: $0.01/hour per endpoint
• • Transit Gateway: $0.05/hour + attachments - Cross-AZ traffic: $0.01/GB

GCP More Predictable

• • Cloud NAT: $0.045/hour (no data processing charge)
• • No endpoint charges
• • No intra-region charges
• • Cross-region uses standard egress pricing

Real-World Architecture Example

Multi-Region App on AWS

# Complexity: High
# Components needed:
- 2 VPCs (us-east-1, eu-west-1)
- 6 subnets (3 AZs × 2 regions)
- 2 Transit Gateways
- Cross-region peering
- Route table updates
- Separate security groups per region

Same App on GCP

# Complexity: Low
# Components needed:
- 1 Global VPC
- 2 regional subnets
- Firewall rules (global)
- Done

Migration Gotchas

AWS → GCP

1. Subnet Model: Can't replicate AZ-specific subnets
2. Security Groups: Redesign using tags/service accounts
3. NACLs: No direct equivalent (use firewall priorities)
4. Route Tables: Less explicit control

GCP → AWS

1. Global VPC: Must split into regional VPCs
2. Firewall Rules: Convert to security groups + NACLs
3. Automatic Routes: Must create explicit route tables
4. Service Account Firewall: Use IAM roles + security groups

Performance Considerations

Latency

• • AWS: Intra-AZ: <1ms, Cross-AZ: 1-2ms, Cross-region: varies
• • GCP: Intra-zone: <1ms, Cross-zone: 1-2ms, Premium tier cross-region: optimized

Throughput

• • AWS: 5 Gbps/instance default, up to 100 Gbps
• • GCP: 2 Gbps/vCPU, up to 32 Gbps standard, 100 Gbps with T4/A2

Decision Framework

Choose AWS VPC When:

• • Need explicit control over network topology
• • Require subnet-level access controls
• • Have existing AWS-heavy infrastructure
• • Want predictable AZ-level isolation

Choose GCP VPC When:

• • Want simpler global networking
• • Need flexible firewall rules
• • Prefer lower operational overhead
• • Building greenfield multi-region apps

Advanced Tips

AWS Pro Tips

1. Use Transit Gateway for hub-spoke topology
2. Implement VPC Flow Logs for security
3. Leverage Local Zones for edge computing
4. Consider AWS Network Firewall for IDS/IPS

GCP Pro Tips

1. Use Shared VPC for organization-wide networking
2. Implement Cloud Armor for DDoS protection
3. Leverage Private Service Connect for service exposure
4. Use hierarchical firewall policies for governance

The Verdict

Neither is universally "better"—they optimize for different use cases:

The best choice depends on your specific requirements, existing expertise, and architectural patterns. Many organizations successfully use both, leveraging each platform's strengths.

Master Cloud Networking with Didaxa

Ready to become a cloud networking expert? Whether you're preparing for AWS Advanced Networking or GCP Professional Cloud Network Engineer certification, Didaxa's AI-powered platform adapts to your learning style. Practice with real scenarios, get instant feedback, and master both platforms with confidence.