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CIDR range definitions

You must specify non-overlapping ranges for the following CIDR ranges.

Machine CIDR ranges cannot be changed after creating your cluster.

OVN-Kubernetes, the default network provider in OpenShift Container Platform 4.14 and later versions, uses the following IP address ranges internally: 100.64.0.0/16, 169.254.169.0/29, 100.88.0.0/16, fd98::/64, fd69::/125, and fd97::/64. If your cluster uses OVN-Kubernetes, do not include any of these IP address ranges in any other CIDR definitions in your cluster or infrastructure.

For OpenShift Container Platform 4.17 and later versions, clusters use 169.254.0.0/17 for IPv4 and fd69::/112 for IPv6 as the default masquerade subnet. These ranges should also be avoided by users. For upgraded clusters, there is no change to the default masquerade subnet.

Machine CIDR

In the Machine classless inter-domain routing (CIDR) field, you must specify the IP address range for machines or cluster nodes.

The default is 10.0.0.0/16. This range must not conflict with any connected networks.

Service CIDR

In the Service CIDR field, you must specify the IP address range for services. The range must be large enough to accommodate your workload. The address block must not overlap with any external service accessed from within the cluster. The default is 172.30.0.0/16.

Pod CIDR

In the pod CIDR field, you must specify the IP address range for pods.

The pod CIDR is the same as the clusterNetwork CIDR and the cluster CIDR. The range must be large enough to accommodate your workload. The address block must not overlap with any external service accessed from within the cluster. The default is 10.128.0.0/14. You can expand the range after cluster installation.

Additional resources

Host Prefix

In the Host Prefix field, you must specify the subnet prefix length assigned to pods scheduled to individual machines. The host prefix determines the pod IP address pool for each machine.

For example, if the host prefix is set to /23, each machine is assigned a /23 subnet from the pod CIDR address range. The default is /23, allowing 510 cluster nodes, and 510 pod IP addresses per node.