Chapter 9. Custom composable networks

The overcloud uses the following pre-defined set of network segments by default:

You can use composable networks to add networks for various services. For example, if you have a network that is dedicated to NFS traffic, you can present it to multiple roles.

Director supports the creation of custom networks during the deployment and update phases. You can use these additional networks for ironic bare metal nodes, system management, or to create separate networks for different roles. You can also use them to create multiple sets of networks for split deployments where traffic is routed between networks.

A single data file (network_data.yaml) manages the list of networks that you want to deploy. Include this file with your deployment command using the -n option. Without this option, the deployment uses the default /usr/share/openstack-tripleo-heat-templates/network_data.yaml file.

Use composable networks to add networks for various services. For example, if you have a network that is dedicated to storage backup traffic, you can present the network to multiple roles.

You can use the following parameters in your network_data.yaml file:

Include the custom network_data.yaml file in your deployment command using the -n option. Without the -n option, the deployment command uses the default set of networks.

You can assign composable networks to the overcloud roles defined in your environment. For example, you might include a custom StorageBackup network with your Ceph Storage nodes.

When you run the openstack overcloud deploy command, include the custom roles_data.yaml file using the -r option. Without the -r option, the deployment command uses the default set of roles with their respective assigned networks.

Each OpenStack service is assigned to a default network type in the resource registry. These services are bound to IP addresses within the network type’s assigned network. Although the OpenStack services are divided among these networks, the number of actual physical networks can differ as defined in the network environment file. You can reassign OpenStack services to different network types by defining a new network map in an environment file, for example, /home/stack/templates/service-reassignments.yaml. The ServiceNetMap parameter determines the network types that you want to use for each service.

For example, you can reassign the Storage Management network services to the Storage Backup Network by modifying the highlighted sections:

parameter_defaults:
  ServiceNetMap:
    SwiftMgmtNetwork: storage_backup
    CephClusterNetwork: storage_backup

Changing these parameters to storage_backup places these services on the Storage Backup network instead of the Storage Management network. This means that you must define a set of parameter_defaults only for the Storage Backup network and not the Storage Management network.

Director merges your custom ServiceNetMap parameter definitions into a pre-defined list of defaults that it obtains from ServiceNetMapDefaults and overrides the defaults. Director returns the full list, including customizations, to ServiceNetMap, which is used to configure network assignments for various services.

Service mappings apply to networks that use vip: true in the network_data.yaml file for nodes that use Pacemaker. The overcloud load balancer redirects traffic from the VIPs to the specific service endpoints.

Enable custom composable networks using one of the default NIC templates. In this example, use the Single NIC with VLANs template (net-single-nic-with-vlans).

For example:

$ openstack overcloud deploy --templates \
    ...
    -n /home/stack/network_data.yaml \
    -r /home/stack/roles_data.yaml \
    -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml \
    -e /usr/share/openstack-tripleo-heat-templates/environments/network-environment.yaml \
    -e /usr/share/openstack-tripleo-heat-templates/environments/net-single-nic-with-vlans.yaml \
    -e /home/stack/templates/service-reassignments.yaml \
    ...

This example command deploys the composable networks, including your additional custom networks, across nodes in your overcloud.

You can use the network_data.yaml file to modify the user-visible names of the default networks:

To change these names, do not modify the name field. Instead, change the name_lower field to the new name for the network and update the ServiceNetMap with the new name.