After completing this section, you should be able to manage the provider and external network configuration and IP addressing needed to launch instances with public access.

Many cloud applications are public-facing services, or have at least one instance requiring public access. A domain operator ensures that existing data center networks are properly configured and available for use by cloud users. The domain operator can advise the cloud user when to choose between a tenant or provider network, and how to appropriately configure DNS and DHCP parameters.

To deploy an instance for public access there are two methods; use a provider network, or use a tenant network that has a routed connection to an external network.

Use a provider network if you have no need for flexibility, or the networking services offered by OpenStack. A tenant network gives you the flexibility to change firewall rules as required, or change the network layout of an application without requiring a network administrator.

External, provider, and tenant networks can be created using the CLI, however you must have administrative privileges to create a provider network.

Use the openstack network create command to create the provider network. The external, shared, provider-network-type, and provider-physical-network options are required.

The --share option allows all projects to use the virtual network. The --external option specifies that the virtual network is external. Not all provider networks are external; the --internal option creates an internal provider network. The --provider-network-type and --provider-physical-network options connect the flat virtual network to the flat physical network.

[user@demo ~(admin)]$ openstack network create \
> --external \
> --share \
> --provider-network-type flat \
> --provider-physical-network datacentre \
> provider-demo
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
...output omitted...
| mtu                       | 1500                                 |
| name                      | provider-demo                        |
| port_security_enabled     | True                                 |
| project_id                | e6b7f37fadf943e1aae06a5c2e55d646     |
| provider:network_type     | flat                                 |
| provider:physical_network | datacentre                           |
| provider:segmentation_id  | None                                 |
| qos_policy_id             | None                                 |
| revision_number           | 6                                    |
| router:external           | External                             |
| segments                  | None                                 |
| shared                    | True                                 |
| status                    | ACTIVE                               |
| subnets                   |                                      |
| tags                      |                                      |
| updated_at                | 2020-07-17T13:44:28Z                 |
+---------------------------+--------------------------------------+

Use the openstack subnet create command to create a subnet for the provider network. Specify the subnet range, DHCP setting, the gateway, the DNS name server, the allocation pool, the network and the subnet name.

[user@demo ~(admin)]$ openstack subnet create \
> --subnet-range 172.25.250.0/24 \
> --no-dhcp \
> --gateway 172.25.250.254 \
> --dns-nameserver 172.25.250.254 \
> --allocation-pool start=172.25.250.101,end=172.25.250.189 \
> --network provider-demo \
> provider-subnet-172.25.250
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| allocation_pools  | 172.25.250.101-172.25.250.189        |
| cidr              | 172.25.250.0/24                      |
| created_at        | 2020-07-17T13:51:02Z                 |
| description       |                                      |
| dns_nameservers   | 172.25.250.254                       |
| enable_dhcp       | False                                |
| gateway_ip        | 172.25.250.254                       |
| host_routes       |                                      |
| id                | 1f5e3ad7-25b0-4e49-ad7e-d6673e2882c9 |
| ip_version        | 4                                    |
| ipv6_address_mode | None                                 |
| ipv6_ra_mode      | None                                 |
| name              | provider-subnet-172.25.250           |
| network_id        | 29840e5f-3c29-4937-b6f8-237b51c21899 |
| project_id        | e6b7f37fadf943e1aae06a5c2e55d646     |
| revision_number   | 0                                    |
| segment_id        | None                                 |
| service_types     |                                      |
| subnetpool_id     | None                                 |
| tags              |                                      |
| updated_at        | 2020-07-17T13:51:02Z                 |
+-------------------+--------------------------------------+

On the Admin tab, navigate to Network → Networks.

Click Create Network to create a new network. Enter provider-demo as the network name. Select a project and a provider network type from the list available. Choose a physical network. If the provider network is to be shared between multiple projects, click Shared. The network can be either internal or external.

Click Next to create the subnet. Provide the subnet name, network address, and a gateway IP. Click Next to make the final settings for the subnet.

Disable or enable DHCP and provide an allocation pool, for example 172.25.250.101,172.25.250.189. Enter a DNS name server, for example 172.25.250.254. Click Create.