Chapter 11. Configuring the SDN

The OpenShift SDN enables communication between pods across the OpenShift cluster, establishing a pod network. Two SDN plug-ins are currently available (ovs-subnet and ovs-multitenant), which provide different methods for configuring the pod network.

For initial advanced installations, the ovs-subnet plug-in is installed and configured by default, though it can be overridden during installation using the os_sdn_network_plugin_name parameter.

For initial quick installations, the ovs-subnet plug-in is installed and configured by default as well, and can be reconfigured post-installation.

Cluster administrators can control pod network settings on masters by modifying parameters in the networkConfig section of the master configuration file (located at /etc/origin/master/master-config.yaml by default):

networkConfig:
  clusterNetworkCIDR: 10.1.0.0/16 
  hostSubnetLength: 8 
  networkPluginName: "redhat/openshift-ovs-subnet" 
  serviceNetworkCIDR: 172.30.0.0/16 

networkConfig:
  clusterNetworkCIDR: 10.1.0.0/16 

  hostSubnetLength: 8 

  networkPluginName: "redhat/openshift-ovs-subnet" 

  serviceNetworkCIDR: 172.30.0.0/16 

Cluster administrators can control pod network settings on nodes by modifying parameters in the networkConfig section of the node configuration file (located at /etc/origin/node/node-config.yaml by default):

networkConfig:
  mtu: 1450 
  networkPluginName: "redhat/openshift-ovs-subnet" 

networkConfig:
  mtu: 1450 

  networkPluginName: "redhat/openshift-ovs-subnet" 

If you are already using one SDN plug-in and want to switch to another:

When switching from the ovs-subnet to the ovs-multitenant plug-in, all the existing projects in the cluster will be fully isolated (assigned unique VNIDs). Cluster administrators can choose to modify the project networks using the administrator CLI.

If a host that is external to OpenShift requires access to the cluster network, you have two options:

Both options are presented as part of a practical use-case in the documentation for configuring routing from an edge load-balancer to containers within OpenShift SDN.