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🚀 What is Google Cloud NAT?

Google Cloud NAT (Network Address Translation) is a fully managed service that enables outbound internet connectivity for resources in private Google Cloud VPC subnets, without requiring external IP addresses.

In simpler terms: Cloud NAT lets VMs without public IPs access the internet (e.g., to install updates or contact APIs), while remaining inaccessible from the outside.

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🧠 Why Use Cloud NAT?

• Secure internet access from private subnets
• No need for bastion hosts or manual NAT gateways
• Supports Compute Engine, GKE nodes, Cloud Run VPC connectors

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🌟 Key Features of Cloud NAT

Feature	Description
No external IPs required	VMs stay private but still access the internet
Managed Service	No need to configure or maintain NAT instances
Scalability	Automatically scales to meet connection demand
High Availability	Fully distributed across zones with regional failover
Logging & Monitoring	Integrated with Cloud Logging and Cloud Monitoring
Per Subnet & Per Instance Controls	Choose which VMs or subnets are NATed
Static IP support	Option to use reserved static IPs for egress
Port Allocation Options	Manual or automatic port management per VM

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🔐 Use Cases

Use Case	Description
Private GKE Clusters	Let GKE nodes access the internet without public IPs
Private Compute VMs	Allow package updates or API calls while remaining internal
Secure Outbound API Access	Talk to third-party APIs without exposing VMs
Avoiding External Attack Surface	Keep services invisible to external scanning tools

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🧰 How to Set Up Cloud NAT — Step-by-Step Tutorial

🧾 Prerequisites

• A GCP project with billing enabled
• A VPC with at least one private subnet
• Compute Engine or GKE nodes without public IPs

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✅ Step 1: Reserve an External Static IP (Optional)

gcloud compute addresses create nat-ip \
    --region=us-central1

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✅ Step 2: Create a Cloud Router

gcloud compute routers create nat-router \
    --network=default \
    --region=us-central1

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✅ Step 3: Create the NAT Configuration

gcloud compute routers nats create nat-config \
    --router=nat-router \
    --region=us-central1 \
    --nat-custom-subnet-ip-ranges=default \
    --nat-external-ip-pool=nat-ip \
    --enable-logging

Explanation:

• nat-custom-subnet-ip-ranges=default → Applies to the default subnet
• nat-external-ip-pool=nat-ip → Uses the static IP created earlier
• --enable-logging → Enables Cloud NAT logs

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✅ Step 4: Test NAT Access

Spin up a VM without a public IP and test:

gcloud compute instances create vm-nat-test \
    --subnet=default \
    --no-address \
    --zone=us-central1-a

gcloud compute ssh vm-nat-test --zone=us-central1-a

Once inside:

curl https://api.ipify.org

You should get the external IP address of your NAT gateway!

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📊 Logging and Monitoring

Enable VPC flow logs and NAT logging to track:

• Number of connections
• Ports used
• Source and destination
• Bandwidth consumption

This is useful for compliance, debugging, and capacity planning.

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🔁 Alternatives to Cloud NAT

Service	Use When
NAT instance (manual)	You need custom firewall/NAT logic
Cloud Proxy (IAP)	For authenticated user access from outside
VPN/Interconnect	For hybrid connectivity, not just internet
AWS NAT Gateway	Equivalent in AWS ecosystem
Azure NAT Gateway	Equivalent in Azure ecosystem

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⚙️ Cloud NAT vs NAT Instance

Feature	Cloud NAT	NAT Instance
Managed	✅	❌
Scalable	✅	🚫 (manually configured)
HA/Failover	✅	❌ (requires manual setup)
Logging	✅	Manual setup needed
Maintenance	None	Requires patching, scaling, monitoring

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🧾 Real-World Example: Private GKE with NAT

A company has a private GKE cluster for running microservices. To access external APIs and pull container updates:

• The nodes have no public IPs
• Cloud NAT + Cloud Router is configured
• No exposure to internet scanners
• Traffic logs are enabled for audit

Outcome:

• Secure architecture
• Reduced operational effort
• Improved compliance posture

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📘 Summary

Capability	Cloud NAT
Enable outbound internet for private VMs	✅
No public IPs required	✅
Fully managed	✅
Works with Compute Engine, GKE, Cloud Run VPC	✅
Logging & Monitoring	✅
Scalable & HA	✅

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✅ Conclusion

Google Cloud NAT is an essential component for securely allowing internet access from private Google Cloud networks. It’s reliable, scalable, and easy to set up — making it a go-to tool in cloud-native and security-conscious environments.