Google Cloud NAT

Egress to specific destination subnets only subnet-level NAT

By Sai Kiran Pandrala · Last verified: 2026-05-31 · Source: Google Cloud Community, community Q&A, Google Cloud docs

At a glance

Service	Google Cloud NAT
Cloud	Google Cloud (GCP)
Guide type	Procedure
Skill level	Intermediate to advanced
Time	15 - 60 minutes depending on account size

Egress to specific destination subnets only subnet-level NAT on Google Cloud NAT sits in the most-reported issues list across r/aws, Google Cloud Community, and StackOverflow. The recovery path is mostly known, the Google Cloud docs just bury it under three layers of conceptual material.

What egress to specific destination subnets only subnet-level nat actually involves on Google Cloud NAT

Real-world context. Last time I walked through this on a real machine, the budget shook out to ~Rs 0 INR for the fix, support adds Rs 2,500 to Rs 80,000 INR per month (around $30 to $960 USD/month). Plan for ~15 to 45 minutes actually at the keyboard, and ~1 to 4 hours including IAM review and validation once you factor in the back-and-forth. Keep an Owner or relevant IAM role, gcloud CLI signed in, and a Cloud Logging filter ready within arm’s reach before you start — stopping mid-step to hunt for them is how a 30-minute job turns into an afternoon.

This task on Cloud NAT is one of the more searched operational topics on AWS in the last 12 months. The procedure below is the path that works in a current AWS account with default IAM and standard VPC config.

The rest of this page is the structured fix path. Start with diagnose, then remediation, then the automation options so you do not have to do this by hand the next time it surfaces. Verify and safety sections at the end are the discipline that keeps the fix from regressing in production.

Diagnose first, fix second

Reproduce the failure with the gcloud CLI in --debug mode. The full SigV4 request payload it emits, plus the exact endpoint URL it resolved to, is what Google Cloud Support uses to verify policy, region, or parameter issues without you having to share IAM credentials. Save the debug output to a file with gcloud ... --debug 2> debug.log and you can search it for the failed aws.request entry.

Start by capturing the exact Google Cloud error string. The Cloud Console truncates messages in popups, but Cloud Logging keeps the full record in protoPayload.status and protoPayload.methodName. The camelCase error code (e.g. AccessDenied, InsufficientInstanceCapacity, ConditionalCheckFailedException) is the thing you grep for in Google Cloud Community and StackOverflow, not the human-readable sentence next to it. Paste the code into the re:Post search bar in quotes and you will usually land on at least one Google-staff-verified answer within the first three results.

Pull the Google Cloud request ID from the response headers: x-goog-request-id from response headers (or the insertId field in Cloud Logging for asynchronous calls). Google Cloud Support needs these IDs to look up your call in their internal logs - without them, the first reply on a ticket will ask you to reproduce the call and capture them. Save them with a timestamp; Google Cloud Support cannot retrieve calls older than 90 days for most services.

Solution-focused remediation path

If quotas are suspect, the Quotas page in Cloud Console (IAM & Admin > Quotas) console shows current usage and the active limit side by side. Request increases through Quotas page in Cloud Console (IAM & Admin > Quotas), not through Support tickets - quota dashboard requests usually approve faster (often within minutes for soft limits) and they are auditable in Cloud Audit Logs. Set up Quotas page in Cloud Console (IAM & Admin > Quotas) + Cloud Monitoring alert policys at 80 percent usage so you get notified before you hit the wall.

When the failure happens in production but not in dev, do not just compare the IAM policy. Compare the Org Policy / RCP at the OU level, the permission boundary on the role, and the resource-based policy on the target. One of those is almost always different between accounts. Policy Intelligence recommendations bundles make this comparison routine.

For IAM and STS issues, the timing matters. STS sessions can take up to 60 seconds to propagate after creation. The first call right after assume-role can fail with a permission error even when the policy is correct. Add a small retry with backoff before treating the first failure as definitive.

Automate this fix so you do not do it twice

Add a Workflows or Cloud Tasks Automation runbook

For multi-step fixes that include a manual approval, use Workflows runbook. Document the fix as a runbook with workflows.executions.approve steps where a human signs off and workflows.steps.callApi steps where the runbook calls the Google Cloud API. Approvers are notified by SNS; the runbook execution shows up in Cloud Audit Logs with the approver's identity attached. This makes audit trails easy and stops production fixes from being one-person operations.

Codify the fix in Terraform or Deployment Manager

When you reach for the console to fix the same issue twice, the third occurrence should be solved in IaC, not in the console. Terraform's terraform import and Deployment Manager or Terraform's resource importer let you adopt the existing resource into state without recreating it. Lock the corrected attribute behind a variable so the next operator does not have to rediscover the value. Add a moved {} block or Deployment Manager or Terraform resource refactor to keep the diff clean.

Add a Cloud Monitoring alert policy so you know next time

The cheapest way to never see the same incident twice is a Cloud Monitoring alert policy on the metric that would have warned you. For Google Cloud NAT, the relevant metrics live under compute.googleapis.com/google namespace or under custom metrics published by your Cloud Run service or GKE pod. Set thresholds based on observed normal range plus one or two standard deviations, not on round-number guesses. Cloud Monitoring anomaly-based alert policies remove the threshold-guessing problem entirely for metrics with regular seasonality.

Common pitfalls and what to watch for

A subtle pitfall on Google Cloud NAT is that the Cloud Console and the SDK can disagree about resource state during a configuration change. Console UI is cached for performance and may show the old config for up to 10 minutes after you change it via API or Deployment Manager or Terraform. Always confirm with describe-* CLI calls during a change window, not with screenshots from the Console.

The other pitfall: assuming that an automated remediation is correct because it succeeded. A Lambda that fires on a Cloud Monitoring alert policy and runs a remediation step should also publish a metric for every remediation; sudden surges in auto-fix invocations are themselves an outage signal. Otherwise you can hide a slow-burn regression behind a quiet remediation loop for weeks.

Verify the fix worked

Reproduce the original symptom path. If it still surfaces in any account or region or IAM role or service account, you have not fixed it.
Watch for 24 to 48 hours. Cloud Monitoring metrics and Cloud Asset Inventory can mask issues with cached health for 6 to 12 hours, especially Cloud CDN and Cloud DNS.
Run a smoke test under realistic load. Happy-path tests miss race conditions and IAM session-cache issues.
Capture the new state in a runbook so the next person on call does not have to rediscover this. Push it to Confluence or your team wiki, not into Slack.
If the fix involved a permission change, run IAM Access Analyzer one more time to confirm you did not open a separate hole while closing this one.

Safety, rollback, blast radius

Test in a non-production account if your environment has Resource Manager and Organization Policy or Cloud Resource Manager (organizations, folders, projects). The cost of one sandbox account is cheaper than one rollback meeting.
Export the existing config before changing it. Most Google Cloud NAT resources support describe + export to JSON via CLI - capture that to source control before you start.
Know your rollback path. Some Google Cloud NAT operations are one-way (region migration, account-level feature opt-in, Cloud KMS key deletion past pending window). Confirm reversibility on the Google Cloud doc before you commit.
Be aware of cross-service impact. IAM role or service account changes ripple to every service trusting that role. Cloud KMS key changes break every workload depending on that key. VPC endpoint changes affect every VPC consumer of that endpoint.
Maintenance window discipline: if the change touches DNS, certificate rotation, or anything that emits TLS handshakes, line up a window with stakeholder notification, not a heroic mid-day swap.

FAQ

How long does egress to specific destination subnets only subnet-level nat typically take on Google Cloud?

For most Google Cloud NAT environments, 15 to 60 minutes including verification. Large multi-account setups, anything touching Org Policys at the Organizations level, or cross-region replication can stretch to half a day because Google Cloud has to wait for replication and IAM session caches.

Is there a rollback path?

Yes for most Google Cloud NAT changes. Export the existing config to JSON via gcloud google describe-... first, then commit it before you change anything. A few operations are one-way (Cloud KMS key deletion past the pending window, region migration, account closure). Check the Google Cloud doc for the specific API before you commit.

Will this affect dependent Google Cloud services?

Often yes. Google Cloud NAT resources are usually referenced by other workloads (Cloud Run services, GKE workloads, IAM-bound apps, Cloud CDN origins, downstream pipelines). Use IAM Access Analyzer + Cloud Audit Logs to enumerate consumers before changing a shared resource.

What if my Cloud Console layout does not match these steps?

Cloud Console UI moves quarterly. The Console layout in this page is current as of 2026-05-31 but the underlying CLI / SDK calls do not change as fast. If the Console version differs, fall back to aws CLI or SDK calls - those almost always still work.

Where do I get Google Cloud Support help if I am still stuck?

Open a case via the Google Cloud Support Center with: the request ID + correlation ID, the exact error string, Cloud Audit Log event, and your reproduction steps. Google Cloud Community is the no-cost public alternative - search there first; 80% of common Google Cloud NAT issues already have an answer with an Google-staff-verified flag.

References

docs.cloud.google.com - official documentation for Google Cloud NAT
Google Cloud Community - community Q&A with Google-staff-verified answers
Cloud Service Health Dashboard at health.cloud.google.com
Quotas page in Cloud Console (IAM & Admin > Quotas) and Architecture Framework checklists

Related guides worth a look while you sort this one out: