External network

The external network typically provides internet access for your instances. By default, this network only allows internet access from instances using Network Address Translation (NAT). You can enable internet access to individual instances using a floating IP address and suitable security group rules. The admin tenant owns this network because it provides external network access for multiple tenants. You must also enable sharing to allow access by those tenants.

	Note
	Perform these commands on the controller node.

To create the external network

Source the admin tenant credentials:
```
$ source admin-openrc.sh
```

Create the network:

$ neutron net-create ext-net --shared --router:external=True
Created a new network:
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | True                                 |
| id                        | 893aebb9-1c1e-48be-8908-6b947f3237b3 |
| name                      | ext-net                              |
| provider:network_type     | gre                                  |
| provider:physical_network |                                      |
| provider:segmentation_id  | 1                                    |
| router:external           | True                                 |
| shared                    | True                                 |
| status                    | ACTIVE                               |
| subnets                   |                                      |
| tenant_id                 | 54cd044c64d5408b83f843d63624e0d8     |
+---------------------------+--------------------------------------+

Like a physical network, a virtual network requires a subnet assigned to it. The external network shares the same subnet and gateway associated with the physical network connected to the external interface on the network node. You should specify an exclusive slice of this subnet for router and floating IP addresses to prevent interference with other devices on the external network.

Replace FLOATING_IP_START and FLOATING_IP_END with the first and last IP addresses of the range that you want to allocate for floating IP addresses. Replace EXTERNAL_NETWORK_CIDR with the subnet associated with the physical network. Replace EXTERNAL_NETWORK_GATEWAY with the gateway associated with the physical network, typically the ".1" IP address. You should disable DHCP on this subnet because instances do not connect directly to the external network and floating IP addresses require manual assignment.

To create a subnet on the external network

Create the subnet:

$ neutron subnet-create ext-net --name ext-subnet \
  --allocation-pool start=FLOATING_IP_START,end=FLOATING_IP_END \
  --disable-dhcp --gateway EXTERNAL_NETWORK_GATEWAY EXTERNAL_NETWORK_CIDR

For example, using 203.0.113.0/24 with floating IP address range 203.0.113.101 to 203.0.113.200:

$ neutron subnet-create ext-net --name ext-subnet \
  --allocation-pool start=203.0.113.101,end=203.0.113.200 \
  --disable-dhcp --gateway 203.0.113.1 203.0.113.0/24
Created a new subnet:
+-------------------+------------------------------------------------------+
| Field             | Value                                                |
+-------------------+------------------------------------------------------+
| allocation_pools  | {"start": "203.0.113.101", "end": "203.0.113.200"}   |
| cidr              | 203.0.113.0/24                                       |
| dns_nameservers   |                                                      |
| enable_dhcp       | False                                                |
| gateway_ip        | 203.0.113.1                                          |
| host_routes       |                                                      |
| id                | 9159f0dc-2b63-41cf-bd7a-289309da1391                 |
| ip_version        | 4                                                    |
| ipv6_address_mode |                                                      |
| ipv6_ra_mode      |                                                      |
| name              | ext-subnet                                           |
| network_id        | 893aebb9-1c1e-48be-8908-6b947f3237b3                 |
| tenant_id         | 54cd044c64d5408b83f843d63624e0d8                     |
+-------------------+------------------------------------------------------+

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