Network requirements
External network requirements
GKE on Bare Metal requires an internet connection for operational purposes. GKE on Bare Metal retrieves cluster components from Container Registry, and the cluster is registered with Connect.
You can connect to Google by using the public internet through HTTPS, a virtual private network (VPN), or a Dedicated Interconnect connection.
Internal network requirements
GKE on Bare Metal can work with Layer 2 or Layer 3 connectivity between cluster nodes, but requires load balancer nodes to have Layer 2 connectivity. The load balancer nodes can be the control plane nodes or a dedicated set of nodes. For more information, see Choosing and configuring load balancers.
The Layer 2 connectivity requirement applies whether you run the load balancer on the control plane node pool or in a dedicated set of nodes.
The requirements for load balancer machines are as follows:
- All load balancers for a given cluster are in the same Layer 2 domain.
- All virtual IP addresses (VIPs) must be in the load balancer machine subnet and routable to the gateway of the subnet.
- Users are responsible to allow ingress load balancer traffic.
Pod networking
GKE on Bare Metal 1.7.0 and later versions allows you to configure up to 250 pods per node. Kubernetes assigns a Classless Inter-Domain Routing (CIDR) block to each node so that each pod can have a unique IP address. The size of the CIDR block corresponds to the maximum number of pods per node. The following table lists the size of the CIDR block that Kubernetes assigns to each node based on the configured maximum pods per node:
| Maximum pods per node | CIDR block per node | Number of IP addresses |
|---|---|---|
| 32 | /26 | 64 |
| 33 – 64 | /25 | 128 |
| 65 – 128 | /24 | 256 |
| 129 - 250 | /23 | 512 |
Running 250 pods per node requires Kubernetes to reserve a /23 CIDR block
for each node. Assuming that your cluster uses the default value of /16
for the clusterNetwork.pods.cidrBlocks field, your cluster has a
limit of (2(23-16))=128 nodes. If you intend to grow the
cluster beyond this limit, you can either increase the value of
clusterNetwork.pods.cidrBlocks or decrease the value of
nodeConfig.podDensity.maxPodsPerNode.
Single user cluster deployment with high availability
The following diagram illustrates a number of key networking concepts for GKE on Bare Metal in one possible network configuration.
Consider the following information to meet the network requirements:
- The control plane nodes run the load balancers, and they all have Layer 2 connectivity, while other connections, including worker nodes, only require Layer 3 connectivity.
- Configuration files define IP addresses for worker node pools.
Configuration files also define VIPs for the following
purposes:
- Services
- Ingress
- Control plane access through the Kubernetes API
- You require a connection to Google Cloud.
Port usage
This section shows how UDP and TCP ports are used on cluster and load balancer nodes.
Control plane nodes
| Protocol | Direction | Port range | Purpose | Used by |
|---|---|---|---|---|
| UDP | Inbound | 6081 | GENEVE Encapsulation | Self |
| TCP | Inbound | 22 | Provisioning and updates of admin cluster nodes | Admin workstation |
| TCP | Inbound | 6444 | Kubernetes API server | All |
| TCP | Inbound | 2379 - 2380 | etcd server client API | kube-apiserver and etcd |
| TCP | Inbound | 10250 | kubelet API | Self and control plane |
| TCP | Inbound | 10251 | kube-scheduler | Self |
| TCP | Inbound | 10252 | kube-controller-manager | Self |
| TCP | Inbound | 10256 | Node health check | All |
| TCP | Both | 4240 | CNI health check | All |
Worker nodes
| Protocol | Direction | Port range | Purpose | Used by |
|---|---|---|---|---|
| TCP | Inbound | 22 | Provisioning and updates of user cluster nodes | Admin cluster nodes |
| UDP | Inbound | 6081 | GENEVE Encapsulation | Self |
| TCP | Inbound | 10250 | kubelet API | Self and control plane |
| TCP | Inbound | 10256 | Node health check | All |
| TCP | Inbound | 30000 - 32767 | NodePort services | Self |
| TCP | Both | 4240 | CNI health check | All |
Load balancer nodes
| Protocol | Direction | Port range | Purpose | Used by |
|---|---|---|---|---|
| TCP | Inbound | 22 | Provisioning and updates of user cluster nodes | Admin cluster nodes |
| UDP | Inbound | 6081 | GENEVE Encapsulation | Self |
| TCP | Inbound | 443* | Cluster management | All |
| TCP | Both | 4240 | CNI health check | All |
| TCP | Inbound | 7946 | Metal LB health check | load balancer nodes |
| UDP | Inbound | 7946 | Metal LB health check | load balancer nodes |
| TCP | Inbound | 10256 | Node health check | All |
* This port can be configured in the cluster config, using the
controlPlaneLBPort field.
Multi-cluster port requirements
In a multi-cluster configuration, added clusters must include the following ports to communicate with the admin cluster.
| Protocol | Direction | Port range | Purpose | Used by |
|---|---|---|---|---|
| TCP | Inbound | 22 | Provisioning and updates of cluster nodes | All nodes |
| TCP | Inbound | 443* | Kubernetes API server for added cluster | Control plane and load balancer nodes |
* This port can be configured in the cluster config, using the
controlPlaneLBPort field.
Configuring firewalld ports
You are not required to disable firewalld to run GKE on Bare Metal on Red
Hat Enterprise Linux (RHEL) or CentOS. To use firewalld, you must open the UDP
and TCP ports used by control plane, worker, and load balancer nodes as described in
Port usage on this page. The following example configurations
show how you can open ports with firewall-cmd, the firewalld command line
utility.
Control plane node example configuration
The following block of commands shows an example of how you can open the needed ports on servers running control plane nodes:
firewall-cmd --permanent --zone=public --add-port=22/tcp
firewall-cmd --permanent --zone=public --add-port=4240/tcp
firewall-cmd --permanent --zone=public --add-port=6444/tcp
firewall-cmd --permanent --zone=public --add-port=6081/udp
firewall-cmd --permanent --zone=public --add-port=10250-10252/tcp
firewall-cmd --permanent --zone=public --add-port=10256/tcp
firewall-cmd --permanent --zone=public --add-port=2379-2380/tcp
firewall-cmd --permanent --zone=public --add-port=443/tcp
firewall-cmd --permanent --zone=public --add-port=30000-32767/tcp
firewall-cmd --permanent --new-zone=k8s-pods
firewall-cmd --permanent --zone=k8s-pods --add-source PODS_CIDR
firewall-cmd --permanent --zone=k8s-pods --set-target=ACCEPT
firewall-cmd --reload
Replace PODS_CIDR with the CIDR blocks reserved for your
pods configured in the clusterNetwork.pods.cidrBlocks field. The default CIDR
block for pods is 192.168.0.0/16.
Worker node example configuration
The following block of commands shows an example of how you can open the needed ports on servers running worker nodes:
firewall-cmd --permanent --zone=public --add-port=22/tcp
firewall-cmd --permanent --zone=public --add-port=4240/tcp
firewall-cmd --permanent --zone=public --add-port=6444/tcp
firewall-cmd --permanent --zone=public --add-port=6081/udp
firewall-cmd --permanent --zone=public --add-port=10250/tcp
firewall-cmd --permanent --zone=public --add-port=10256/tcp
firewall-cmd --permanent --zone=public --add-port=443/tcp
firewall-cmd --permanent --zone=public --add-port=30000-32767/tcp
firewall-cmd --permanent --new-zone=k8s-pods
firewall-cmd --permanent --zone=k8s-pods --add-source PODS_CIDR
firewall-cmd --permanent --zone=k8s-pods --set-target=ACCEPT
firewall-cmd --reload
Replace PODS_CIDR with the CIDR blocks reserved for your
pods configured in the clusterNetwork.pods.cidrBlocks field. The default CIDR
block for pods is 192.168.0.0/16.
Load balancer node example configuration
The following block of commands shows an example of how you can open the needed ports on servers running load balancer nodes:
firewall-cmd --permanent --zone=public --add-port=22/tcp
firewall-cmd --permanent --zone=public --add-port=4240/tcp
firewall-cmd --permanent --zone=public --add-port=6444/tcp
firewall-cmd --permanent --zone=public --add-port=7946/tcp
firewall-cmd --permanent --zone=public --add-port=7946/udp
firewall-cmd --permanent --zone=public --add-port=6081/udp
firewall-cmd --permanent --zone=public --add-port=10250/tcp
firewall-cmd --permanent --zone=public --add-port=10256/tcp
firewall-cmd --permanent --zone=public --add-port=443/tcp
firewall-cmd --permanent --zone=public --add-port=30000-32767/tcp
firewall-cmd --permanent --new-zone=k8s-pods
firewall-cmd --permanent --zone=k8s-pods --add-source PODS_CIDR
firewall-cmd --permanent --zone=k8s-pods --set-target=ACCEPT
firewall-cmd --reload
Replace PODS_CIDR with the CIDR blocks reserved for your
pods configured in the clusterNetwork.pods.cidrBlocks field. The default CIDR
block for pods is 192.168.0.0/16.