AWS vs. GCP: Virtual Private Cloud (VPC) Networking Comparison
Understanding the differences between AWS and GCP VPC networking is essential for designing scalable and secure cloud architectures. Below is a detailed comparison of how VPCs behave and are configured across both platforms.
1. VPC Scope
- AWS: VPCs are regional, meaning they are confined to a specific AWS region.
- GCP: VPCs are global, allowing subnets to span across regions under a single VPC.
2. CIDR Assignment
- AWS: A VPC is assigned one or more CIDR blocks, and its subnets must fall within those CIDRs.
- GCP: The VPC does not have CIDR blocks of its own. Only subnets have CIDRs.
3. Subnet Design
- AWS: Subnets are zonal (confined to a single Availability Zone).
- GCP: Subnets are regional (span across all zones in a region).
✅ Result: You typically create fewer, larger subnets in GCP than in AWS.
4. Public vs. Private Subnet Configuration
-
AWS: Subnet type (public/private) depends on its default route:
- Internet Gateway (IGW) for public
- NAT Gateway for private
-
GCP: Subnet config remains the same. You control public access at the resource level by choosing whether or not to assign a public IP.
✅ GCP also offers VPC-level firewalls and Organizational Policies to control or prevent the use of public IPs, effectively enforcing subnet privacy.
5. Firewalling and Access Control
-
AWS:
-
NACLs: Assigned to subnets
-
Security Groups: Assigned to Network Interface Card (NIC)
-
Security Group rules can reference other SGs, allowing dynamic, identity-based firewalling.
-
-
GCP:
- Firewall rules are applied at the VPC level.
- Firewall rules use Tags to match resources dynamically (similar to SG referencing).
-
Two types of tags:
- Secure Tags (
--purpose=GCE_FIREWALL) - IAM-governed - Network Tags - classic tagging for firewall rule matching
- Secure Tags (
6. Private API Access
- AWS: Requires configuration of VPC Endpoints per service.
- GCP: Simply enable Private Google Access at the subnet level.
7. Routing Options
- GCP: Allows choice between regional and global routing at the VPC level.
8. Auto Mode VPC (GCP)
-
GCP offers an optional auto mode VPC setup:
- Creates a /20 subnet (4,096 IPs) in every region.
- Uses 10.128.0.0/9 address space, allocating each region from this block.
⚠️ Auto mode VPCs are convenient for startups or quick setups but may cause IP overlap or scalability issues for larger environments.
In GCP, VPCs have an optional “auto” mode which will create a single /20 (4,096 IP) subnet in every region, with each region’s CIDR coming from a pre-determined set of IP CIDRs — all of which fall within the 10.128.0.0/9 block (10.128.0.1–10.255.255.254)
- Both the limited 4096 IPs per region as well as the fact it takes the upper half of the huge 10.0.0.0/8 private IP range (that you ideally would need to evacuate to avoid overlap in any of your other environments) means this usually isn’t a good choice for many larger or more established businesses — but it is a fast and easy way to get started in a startup.
Summary
| Feature | AWS | GCP |
|---|---|---|
| VPC Scope | Regional | Global |
| VPC CIDR | Required | Not used (subnets only) |
| Subnet Scope | Zonal | Regional |
| Public IP Control | Subnet Route + NAT/IGW | Resource-level IP assignment + Firewall |
| Firewall Rules | NACLs + SGs | VPC-level rules + Tags |
| Private API Access | VPC Endpoints | Private Google Access |
| Routing Options | Regional | Regional or Global |
| Auto Mode | N/A | Yes (with limitations) |
Use this guide to choose the right networking strategy based on your scale, performance, and security requirements across AWS and GCP.