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 dedicated to NFS traffic, you can present it to multiple roles.

Director supports the creation of custom networks during the deployment and update phases. These additional networks can be used 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 to be deployed. Include this file with your deployment command using the -n option. Without this option, the deployment uses the default file (/usr/share/openstack-tripleo-heat-templates/network_data.yaml).

This procedure shows you how to add an additional composable network to your overcloud.

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

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

This procedure shows you how to add composable networks to a role in your overcloud.

When running the openstack overcloud deploy command, include the roles_data 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 then 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 used 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 you only need to define a set of parameter_defaults for the Storage Backup network and not the Storage Management network.

The director merges your custom ServiceNetMap parameter definitions into a pre-defined list of defaults taken from ServiceNetMapDefaults and overrides the defaults. The director returns the full list, including customizations back 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 file for nodes that use Pacemaker. The overcloud’s load balancer redirects traffic from the VIPs to the specific service endpoints.

This procedure shows you how to enable custom composable networks using one of the default NIC templates. In this case, it is the Single NIC with VLANs (single-nic-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.