Setting up intranode visibility

This guide shows you how to set up intranode visibility in a Google Kubernetes Engine (GKE) cluster, so that all network traffic in your cluster is seen by the Google Cloud network.

Intranode visibility allows you to:

• See flow logs for all traffic between Pods, including traffic between Pods on the same node.
• Create firewall rules that apply to all traffic among Pods, even Pods on the same node.
• Use Packet Mirroring to clone traffic between Pods on the same node and forward it for examination.

When a Pod sends a packet to another Pod on the same node, the packet leaves the node and is processed by the Google Cloud network. Then the packet is immediately sent back to the same node and forwarded to the destination Pod.

Intranode visibility is disabled by default.

Intranode visibility is required if you want your cluster to use a VPC network whose MTU is 1500 bytes. In addition, the cluster's GKE version must be 1.15 or higher. For more information on 1500 MTU VPC networks, see Maximum transmission unit in the VPC documentation.

Things to consider

Increased log volume

When intranode visibility is enabled, flow log volume may increase with more traffic being captured by the VPC. You can manage the costs associated with flow logging by adjusting the logging settings.

All Pod-to-Pod traffic is subject to firewalls

All traffic among Pods, including Pods deployed to the name node, is visible to the VPC when intranode visibility is enabled. Enabling intranode visibility might cause previously unrestricted traffic to be subject to firewall rules. Evaluate your node-level firewalls using Connectivity Tests to ensure that legitimate traffic is not obstructed.

Before you begin

Before you start, make sure you have performed the following tasks:

• Ensure that you have enabled the Google Kubernetes Engine API.
Enable Google Kubernetes Engine API
• Ensure that you have installed the Cloud SDK.

Set up default gcloud settings using one of the following methods:

• Using gcloud init, if you want to be walked through setting defaults.
• Using gcloud config, to individually set your project ID, zone, and region.

Using gcloud init

If you receive the error One of [--zone, --region] must be supplied: Please specify location, complete this section.

1. Run gcloud init and follow the directions:

   gcloud init

   If you are using SSH on a remote server, use the --console-only flag to prevent the command from launching a browser:

   gcloud init --console-only

2. Follow the instructions to authorize gcloud to use your Google Cloud account.
3. Create a new configuration or select an existing one.
4. Choose a Google Cloud project.
5. Choose a default Compute Engine zone.

Note: You can override these default settings in gcloud commands using the --project, --zone, and --region flags.

Using gcloud config

• Set your default project ID:

  gcloud config set project PROJECT_ID

• If you are working with zonal clusters, set your default compute zone:

  gcloud config set compute/zone COMPUTE_ZONE

• If you are working with regional clusters, set your default compute region:

  gcloud config set compute/region COMPUTE_REGION

• Update gcloud to the latest version:

  gcloud components update

Note: You can override these default settings in gcloud commands using the --project, --zone, and --region flags.

Tasks overview

To demonstrate setting up intranode visibility, here's an overview of the tasks that you perform:

1. Enable flow logs for the default subnet in the us-central1 region.
2. Create a single-node cluster that has intranode visibility enabled.
3. Create two Pods in your cluster.
4. Send an HTTP request from one Pod to the other Pod.
5. View the flow log entry for the Pod-to-Pod request.

Examples in this guide use:

• us-central1 as the default region.
• us-central1-a as the default zone.

Enabling flow logs for a subnet

You can enable flow logs for a subnet using the gcloud tool or the Google Cloud Console.

gcloud

1. Enable flow logs for the default subnet in the us-central1 region:

   gcloud compute networks subnets update default --region us-central1 \
       --enable-flow-logs
   

2. Verify that your subnet has flow logs enabled:

   gcloud compute networks subnets describe default --region us-central1
   

   The output shows that flow logs are enabled:

   ...
   enableFlowLogs: true
   ...
   ipCidrRange: 10.128.0.0/20
   region: https://www.googleapis.com/compute/v1/projects/abc-712099/regions/us-central1
   

Console

1. Visit the Google Kubernetes Engine VPC networks page in Cloud Console.

   Visit the VPC networks page

2. In the us-central1 row, click default.

3. Click Edit.

4. Under Flow logs, select On.

5. Click Save.

Creating a cluster with intranode visibility enabled

You can create a cluster that has intranode visibility enabled using the gcloud tool or the Google Cloud Console.

gcloud

Create a single-node cluster that has intranode visibility enabled:

gcloud container clusters create cluster-name \
    --zone us-central1-a \
    --num-nodes 1 \
    --enable-intra-node-visibility

Console

1. Visit the Google Kubernetes Engine menu in Cloud Console.

   Visit the Google Kubernetes Engine menu

2. Click Create.

3. Enter the Name for your cluster.

4. For the Location type, select Zonal.

5. In the Zone drop-down list, select us-central1-a.

6. From the navigation pane, under Node Pools, click default-pool.

7. Enter a Name for the node pool.

8. Choose the Node version for your node.

9. For the Number of nodes, enter 1.

10. From the navigation pane, under Cluster, click Networking.

11. Select the Enable intranode visibility checkbox.

12. Click Create.

Getting credentials for your cluster

Get the credentials for your new cluster:

gcloud container clusters get-credentials cluster-name \
    --zone us-central1-a

The credentials are saved in your kubeconfig file, which is typically at $HOME/.kube/config.

Creating two Pods

1. For the first Pod, create a file named pod-1.yaml based on the following sample manifest:

   apiVersion: v1
   kind: Pod
   metadata:
     name: pod-1
   spec:
     containers:
     - name: container-1
       image: gcr.io/google-samples/hello-app:2.0
   

2. Create the Pod by running the following command:

   kubectl apply -f pod-1.yaml
   

3. For the second Pod, create a file named pod-2.yaml based on the following sample manifest:

   apiVersion: v1
   kind: Pod
   metadata:
     name: pod-2
   spec:
     containers:
     - name: container-2
       image: gcr.io/google-samples/node-hello:1.0
   

4. Create the Pod by running the following command:

   kubectl apply -f pod-2.yaml
   

5. View the Pods:

   kubectl get pod pod-1 pod-2 --output wide
   

   The output shows the IP addresses of your Pods. Make a note of these addresses.

   NAME      READY     STATUS    RESTARTS   AGE       IP           ...
   pod-1     1/1       Running   0          1d        10.52.0.13   ...
   pod-2     1/1       Running   0          1d        10.52.0.14   ...
   

Sending a request from pod-1 to pod-2

1. Get a shell to the container in pod-1:

   kubectl exec -it pod-1 sh
   

2. In your shell, send a request to pod-2:

   wget -qO- pod-2-ip-address:8080
   

   where pod-2-ip-address is the IP address of pod-2 that you noted earlier.

   The output shows the response from the container running in pod-2:

   Hello Kubernetes!
   

3. Type exit to leave the shell and return to your main command-line environment.

Viewing flow log entries

You can view flog log entries using the gcloud tool or the Google Cloud Console.

gcloud

View a flow log entry for the request from pod-1 to pod-2:

gcloud logging read \
    'logName="projects/project-id/logs/compute.googleapis.com%2Fvpc_flows" AND jsonPayload.connection.src_ip="pod-1-ip-address"'

where:

• project-id is your project ID.
• pod-1-ip-address is the IP address of pod-1.

The output shows a flow log entry for a request from pod-1 to pod-2. In this example, pod-1 has IP address 10.56.0.13, and pod-2 has IP address 10.56.0.14.

...
jsonPayload:
  bytes_sent: '0'
  connection:
    dest_ip: 10.56.0.14
    dest_port: 8080
    protocol: 6
    src_ip: 10.56.0.13
    src_port: 35414
...

Console

1. Visit the Google Kubernetes Engine Stackdriver logs page in Cloud Console.

   Visit the Stackdriver logs page

2. At the top of the page, in the filter box, at the right, click the down arrow, and select Convert to advanced filter.

3. Delete any text that is in the filter box, and enter this query:

   resource.type="gce_subnetwork"
   logName="projects/project-id/logs/compute.googleapis.com%2Fvpc_flows"
   jsonPayload.connection.src_ip="pod-1-ip-address"
   

   where:

   • project-id is your project ID.
   • pod-1-ip-address is the IP address of pod-1.

4. Expand the log entry that appears. Under jsonPayload you can see that the request was sent from pod-1 to pod-2. In the following example, pod-1 has an IP address of 10.56.0.13, and pod-2 has an IP address of 10.56.0.14.

   jsonPayload: {
     bytes_sent:  "0"
     connection: {
       dest_ip:  "10.56.0.14"
       dest_port:  8080
       protocol:  6
       src_ip:  "10.56.0.13"
       src_port:  35414
   

Recall that your cluster has only one node. So pod-1 and pod-2 are on the same node. Even so, flow log entries are available for the intranode communication between pod-1 and pod-2.

Enabling intranode visibility on an existing cluster

You can enable intranode visibility for an existing cluster using the gcloud tool or the Google Cloud Console.

gcloud

gcloud beta container clusters update cluster-name \
    --enable-intra-node-visibility

where cluster-name is the name of your existing cluster.

Console

1. Visit the Google Kubernetes Engine menu in Cloud Console.

   Visit the Google Kubernetes Engine menu

2. Click the cluster's edit button , which looks like a pencil.

3. Enable Intranode visibility.

4. Click Save.

When you enable intranode visibility for an existing cluster, components in both the control plane and the worker nodes are restarted.

Warning: If you are using maintenance windows, intranode visibility will not be enabled until a maintenance window occurs. If you prefer not to wait, you can manually "upgrade" the node pool to the same version it is already using, by setting the --cluster-version flag to the same GKE version the control plane is already running. You must use the gcloud command if you use this workaround. See the caveats section of the maintenance window documentation for more information.

After you've enabled this feature, you can confirm it's activated by examining the routing rules on your node:

1. Show the IP rules:

   ip rule show
   

   The output looks similar to this:

   0:  from all lookup local
   30001:  from all fwmark 0x4000/0x4000 lookup main
   30002:  from all iif lo lookup main
   30003:  not from all iif eth0 lookup 1
   32766:  from all lookup main
   32767:  from all lookup default
   

2. Show the IP routes:

   ip route show table 1
   

   The output looks similar to this:

   default via GKE-node-subnet-gw dev eth0
   

Disabling intranode visibility

You can disable intranode visibility for an existing cluster using the gcloud tool or the Google Cloud Console.

gcloud

gcloud beta container clusters update cluster-name \
    --no-enable-intra-node-visibility

where cluster-name is the name of your existing cluster.

Console

1. Visit the Kubernetes clusters page in Cloud Console.

   Visit Kubernetes clusters page

2. Click the cluster's edit button , which looks like a pencil.

3. From the Intranode visibility drop-down menu, select Disabled.

4. Click Save.

When you disable intranode visibility for an existing cluster, components in both the control plane and the worker nodes are restarted.

Warning: If you are using maintenance windows, intranode visibility will not be disabled until a maintenance window occurs. If you prefer not to wait, you can manually "upgrade" the node pool to the same version it is already using, by setting the --cluster-version flag to the same GKE version the control plane is already running. You must use the gcloud command if you use this workaround. See the caveats section of the maintenance window documentation for more information.

Restrictions

Clusters with intranode visibility enabled have the following restrictions:

• If you enable intranode visibility, and use ip-masq-agent configured with the nonMasqueradeCIDRs parameter, the nonMasqueradeCIDRs needs to include the Pod CIDR, otherwise you can experience intranode connectivity issues.

What's next

• Learn how to control the communication between your cluster's Pods and Services by creating a cluster network policy.

• Learn about the benefits of Google Cloud alias IP ranges in VPC-native clusters.