I have a microservice in a gke cluster that I need to communicate with an external third party service and for that I need the ip of that microservice to be maintained even if the node restarts and the ip changes. The cluster is public and I have tried configuring cloud nat with a static ip in the network where the cluster is deployed but I can’t get it to show me the cloud nat static ip inside the pod. Has anyone achieved it in a standard public gke cluster? All help will be well received 
Absolutely, maintaining a stable IP for your microservice in a GKE cluster while communicating with an external third-party service is a common requirement. It seems like you’re on the right track with using Cloud NAT and a static IP, but there might be some configuration nuances to address.
Here’s a step-by-step guide to achieving this setup in a standard public GKE cluster:
- Static IP Setup:
- Create a static external IP address in Google Cloud Console. Make sure it’s in the same region as your GKE cluster.
- Note down the IP address as you’ll need it later.
- Network Configuration:
- Check that your GKE cluster and the service needing a static IP are in the same network.
- The GKE cluster’s nodes should be in the same VPC (Virtual Private Cloud) as the service.
- You can use subnets to ensure that the IP address you’ve assigned can be accessed from within the GKE cluster.
- Service Configuration:
- In your microservice’s deployment configuration, make sure to expose it using a Kubernetes
Serviceof typeLoadBalancer. - Specify the static IP you created as the
loadBalancerIPin theServiceconfiguration.
- Firewall Rules:
- Ensure that firewall rules allow traffic from the GKE nodes to the external third-party service.
- GKE nodes are assigned IP addresses from the same subnet, so make sure this traffic isn’t blocked.
- Cloud NAT Configuration:
- Set up a Cloud NAT gateway in your VPC.
- Associate the NAT gateway with the subnet where your GKE nodes reside.
- Make sure you configure the NAT gateway to use the static IP you created earlier.
- Pod Configuration:
- Within your pods, you should be able to reach the external third-party service using the static IP assigned to your NAT gateway.
- You won’t necessarily see the Cloud NAT static IP directly from within the pod; you’ll need to use DNS to resolve the external service’s hostname to this IP.
- DNS Resolution:
- Use DNS to resolve the hostname of the external third-party service to the static IP of the NAT gateway.
- This means that your microservice code should communicate with the third-party service using its hostname, not its IP.
Remember that GKE node IPs might change if nodes are recreated, which is common in an autoscaled environment, but the IP of the NAT gateway should remain stable.
Lastly, if you’re having issues seeing the Cloud NAT static IP inside the pod, ensure that your pod’s network settings are properly configured and that DNS resolution is functioning correctly.
By following these steps, you should be able to maintain a stable IP for your microservice in a GKE cluster even if the underlying nodes restart and their IPs change.
Hello AIAvenue, first of all, thank you very much for your quick response!
I have tried to follow the steps you mention and when creating a loadbalancer service associated with the microservice with the static ip, the service stays in the pending state because it says that the ip is being used by another resource. In this case, the resource that is using it is the cloud router of the cloud nat. I have tried to do it the other way around, create the service with another new static ip, and reconfigure the cloud nat with that ip once the service has been created and it tells me that cloud nat cannot be created because the ip is being used by another resource.
Hi Nortena,It seems like you are encountering conflicts with IP address allocation in your cloud environment. Here are some steps you can take to troubleshoot and resolve the issue:
Review Existing Resources: Double-check all the resources that might be using the IP address in question. In your case, it’s the IP address associated with your microservice load balancer and the Cloud NAT. Ensure that there are no overlapping IP allocations.
Release and Reallocate IP: If you are certain that the IP address is not being used elsewhere, try releasing the IP address from the Cloud NAT or any other resource that’s using it. Once released, you can try allocating it to the load balancer service.
IP Address Reservation: Some cloud providers allow you to reserve IP addresses for specific resources. If the IP address is critical for your microservice, you might want to consider reserving it to ensure that it’s always available for your service.
Check Subnet and Region: Make sure that the IP address you are trying to allocate is within the correct subnet and region for your microservice and other resources. IP addresses are often associated with specific subnets and regions.
Retry in Different Order: As you mentioned, you tried creating the service first and then the NAT, and vice versa. Sometimes, the order in which resources are created can impact IP address allocation. You could experiment with creating resources in a different order to see if that resolves the issue.
Contact Cloud Provider Support: If you’ve tried all of the above steps and are still facing issues, it might be a good idea to reach out to your cloud provider’s support team. They can look into the specifics of your environment and help you troubleshoot the problem more effectively.
Check Documentation and Release Policies: Review the documentation provided by your cloud provider regarding IP address allocation, release policies, and restrictions. It’s possible that there are specific rules or limitations that are causing the issue.
Consider Dynamic IPs: If the static IP allocation continues to be problematic, you might consider using dynamic IPs for your microservice. While static IPs have advantages, dynamic IPs could potentially alleviate the allocation conflicts.
Remember that each cloud provider has its own intricacies and behaviors when it comes to IP address allocation and resource management. Make sure you are following the best practices and guidelines provided by your cloud provider’s documentation.
As he commented, he changed the order of execution and deleted the cloud nat to free the static IP and created a loadbalancer type service associated with the microservice at that static IP but when trying to create the cloud nat with that static IP the same thing happens, which does not allow it to be created with that ip because it is being used by the loadbalancer type service. That’s why I don’t understand your initial steps that tell me to use the same IP for the service as for the cloud nat because it doesn’t work.
I apologize for any confusion in my initial response. It seems there might have been a misunderstanding regarding IP allocation. If you’re encountering issues where an IP address is being used by a load balancer and you’re unable to assign the same IP to a Cloud NAT instance, let’s clarify the steps:
-
IP Allocation: When using a static IP for both a Cloud NAT instance and a load balancer, it’s important to ensure that the IP address is not allocated or in use by any other resource. If the IP is already allocated to a load balancer, you won’t be able to assign it to Cloud NAT simultaneously.
-
Load Balancer IPs: If you have allocated the static IP to a load balancer service, you should not attempt to assign the same IP to Cloud NAT. In Google Cloud, IP addresses are a shared resource, and the same IP cannot be assigned to multiple resources at the same time.
-
Separate IPs: If you require both a Cloud NAT instance and a load balancer service to have their own dedicated IP addresses, you will need to allocate separate static IP addresses for each resource.
Given your scenario, if you want to have both a Cloud NAT instance and a load balancer, you would need to allocate separate static IPs for them. You cannot use the same IP for both resources simultaneously due to IP address allocation constraints.
Here’s a revised suggestion:
-
Allocate Separate IPs: Allocate a static IP for your Cloud NAT instance and a separate static IP for your load balancer.
-
Update Configurations: Update your configurations to use the appropriate IPs for each resource. Make sure your Cloud NAT configuration uses the dedicated IP you allocated for it, and your load balancer configuration uses the separate dedicated IP.
-
Verify Connectivity: After allocating separate IPs and updating your configurations, verify that your Cloud NAT instance and load balancer are working as intended.
Remember that Google Cloud’s IP address management requires distinct IPs for each resource to avoid conflicts. If you’re encountering any specific issues during these steps, it’s recommended to refer to Google Cloud documentation or seek support to ensure accurate configuration based on your exact use case.
Thank you very much for the answer, actually I’m thinking that I shouldn’t need a loadbalancer service for the microservice because I don’t have to expose it, it’s the microservice that has to communicate with the service outside the cluster and not the other way around.
I also think that being a public cluster gke shouldn’t need to use cloud nat but I can’t find a way for the microservice to exit through a static ip instead of the node’s ip that can change if the node restarts. I can’t find a solution, my cluster is a standard public gke
If your microservice needs to communicate with services outside the cluster and you don’t need to expose your microservice to external traffic, you might not need a LoadBalancer service. Instead, you can use a Service of type ClusterIP, which exposes the service within the cluster but not externally.
Regarding the issue of your microservice needing to exit through a static IP instead of the node’s IP, here are a few options to consider:
-
Egress Gateway with Node Pools: You can create a dedicated node pool with nodes that have static external IPs assigned. Then, configure your microservice to run on this specific node pool. This way, the egress traffic from your microservice will consistently use the same static external IP.
-
External NAT Gateway: While Google Kubernetes Engine (GKE) public clusters generally use the nodes’ IPs for egress traffic, you can set up an External NAT Gateway which allows your egress traffic to use a static IP address. This can be achieved by configuring a Cloud NAT gateway and directing your egress traffic through it. This way, regardless of which node your microservice is running on, the traffic will exit through the static IP associated with the NAT gateway.
-
External Service: If your microservice needs to access external services (not within your GKE cluster) and you want to control the egress IP, you can deploy a separate application in your cluster that acts as a proxy. This proxy can use a static IP or a NAT gateway, and your microservice communicates with this proxy instead of directly with external services.
-
Service Mesh: Using a service mesh like Istio or Linkerd can provide advanced control over your microservices’ communication, including egress traffic. These tools allow you to configure egress gateways and control the egress IP addresses for your services.
Remember that the choice between these options depends on your specific requirements, infrastructure setup, and desired level of control over egress traffic. It’s also worth noting that some of these solutions might have associated costs or complexity, so you should carefully evaluate the trade-offs before implementing any of them in your environment.
Thank you very much for your answer, this what you comment in point 2 “External NAT gateway: while public Google Kubernetes Engine (GKE) clusters generally use the IPs of the nodes for egress traffic, you can configure a gateway External NAT binding that allows your egress traffic to use a static IP address.This can be achieved by setting up a NAT gateway in the cloud and directing your egress traffic through it.This way regardless of the node you are on the microservice runs, the traffic will exit through the static IP associated with the NAT gateway.” It is what I have configured but it is not working as I expect. Reserved a static ip and created a cloud nat and a cloud router on the same “default” network that created the cluster and assigned the cloud nat the static ip. But when I go inside the microservice and run “curl https://ipinfo.io/ip” I still see the node ip instead of the cloud nat ip, the static one I have associated. Can you think of what I might be missing?
Same for me too. Did the same steps as yours, and when doing a curl from inside the microservice, I get the nodeip.
Refer to my article which explains how to run private nodes in public GKE cluster and use cloud NAT for private nodes Internet access. This will allow you to run the microservice on the private nodes and get a static external IP with cloud NAT for outbound connections. Also refer to the limitations.
https://chimbu.medium.com/private-node-pools-in-standard-public-gke-clusters-9190ff62bef
Egress Gateway with Node Pools:
Can you pls point me to the docs for this setup ^
Cheers,
/M