Using Private NAT to Resolve Network IP Address Overlap
Running AI Workloads in Hybrid Environments
Running AI workloads across your data center and the cloud requires a sophisticated, global network that unifies cloud and on‑premises resources.
Google Cloud WAN delivers this unified networking fabric — connecting VPCs, data centers, and specialized hardware — but also exposes a common challenge: IPv4 address scarcity and overlapping subnets.
When enterprises merge private and cloud environments, manually resolving these conflicts can become operationally complex.
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IPv4 Address Constraints and Solutions
IPv4 address conflicts are a long‑standing networking issue, now intensified by IP‑intensive workloads and applications.
Google Cloud offers several solutions to address private IP constraints between non‑routable networks:
- Private Service Connect (PSC)
- IPv6 addressing
- Network Address Translation (NAT) appliances
In this article, we focus on Private NAT — part of the Cloud NAT service — which enables seamless private‑to‑private connectivity across overlapping IP ranges without custom routing or managing proprietary NAT infrastructure.
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Understanding Private NAT
Private NAT allows Google Cloud resources to connect to other VPC networks or on‑premises networks with overlapping/non‑routable subnets.
Key Benefits
- Seamless connectivity across conflicting IP spaces
- No manual infrastructure management — fully managed by Google Cloud
- Scalable and reliable service
- Compatible with hybrid and multi‑cloud architectures
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For complex workloads like AI applications operating across cloud and on‑prem environments, address overlap resolution is critical for scalability and performance.
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Service Highlights
- Managed Service: Google Cloud handles NAT gateway infrastructure, reducing operational burden.
- Simplified Management: Centralized mechanism for private‑to‑private communication.
- High Availability: Distributed design with VM‑to‑VM line‑rate performance and resiliency.
- Scalability: Automatically scales NAT IPs and concurrent connections.
Figure: Cloud NAT options
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Common Use Cases
1. Global Network Unification with Network Connectivity Center
Private NAT enables connections between networks using overlapping non‑routable IP ranges.
- VPC Spoke‑to‑Spoke: Private communication between VPC networks with overlapping subnets.
- VPC‑to‑Hybrid Spoke: Connectivity between a cloud VPC and an on‑premises hybrid spoke via Cloud Interconnect or VPN.
- Learn more.
Figure: Private NAT with Network Connectivity Center
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2. Local Hybrid Connectivity in Shared VPC
Shared VPC architectures can use a single private NAT gateway for destination routes across all workloads in the VPC.
> “Private NAT let us connect our Orange on‑prem data center with the Masmovil GCP environment despite IP overlaps — ensuring business continuity without changing our environment.”
— Pedro Sanz Martínez, Head of Cloud Platform Engineering, MasOrange
Figure: Local hybrid connectivity using private NAT
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3. Cloud Run and GKE Workloads
Private NAT ensures secure outbound access for Cloud Run and GKE workloads without exposing them to the public internet — especially useful for non‑RFC 1918 ranges (e.g., Class E) often used to overcome IPv4 exhaustion.
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Configuration in Action
Example Scenario: Connecting to a Partner Network with Overlapping IPs
Situation:
Your `production-vpc` has a subnet `app-subnet-prod` (`10.20.0.0/24`).
The partner’s network also uses `10.20.0.0/24` — causing an IP conflict.
Solution:
Configure Private NAT to translate traffic from `app-subnet-prod` before sending it through the VPN tunnel.
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Step‑by‑Step Setup
1. Create a dedicated subnet for NAT IPs
This subnet must not overlap with source or destination ranges.
gcloud compute networks subnets create pnat-subnet-prod \
--network=production-vpc \
--range=192.168.1.0/24 \
--region=us-central1 \
--purpose=PRIVATE_NAT---
2. Create a Cloud Router
gcloud compute routers create prod-router \
--network=production-vpc \
--region=us-central1---
3. Create a Private NAT Gateway
Only traffic from `app-subnet-prod` to local hybrid endpoints will be translated.
gcloud compute routers nats create pnat-to-partner \
--router=prod-router \
--region=us-central1 \
--type=PRIVATE \
--nat-custom-subnet-ip-ranges=app-subnet-prod:ALL
gcloud compute routers nats rules create 1 \
--router=prod-router --region=us-central1 \
--nat=pnat-to-partner \
--match='nexthop.is_hybrid' \
--source-nat-active-ranges=pnat-subnet-prod---
Result
VMs in `app-subnet-prod` sending traffic to the partner’s overlapping network will have source IPs translated to `192.168.1.0/24`, avoiding conflicts.
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Conclusion
Google Cloud Private NAT solves the challenge of connecting networks with overlapping IP address spaces — offering a fully managed, scalable, and highly available solution for complex hybrid and multi‑cloud environments.
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Learn More
- Private NAT Documentation: cloud.google.com/nat/docs/private-nat
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