9.3. Creating virtual subnets¶

POST /v2.0/subnets

Create a subnet in a network.

OpenStack Networking does not try to derive the correct IP version from the CIDR. If you do not specify the gateway_ip attribute, OpenStack Networking allocates an address from the CIDR for the gateway for the subnet.

To specify a subnet without a gateway, set the gateway_ip attribute to null in the request body. If you do not specify the allocation_pools attribute, OpenStack Networking automatically allocates pools for covering all IP addresses in the CIDR, excluding the address reserved for the subnet gateway. Otherwise, you can explicitly specify allocation pools as shown in the following example.

When you specify both the allocation_pools and gateway_ip attributes, you must ensure that the gateway IP does not overlap with the allocation pools; otherwise, the call returns the Conflict (409) response code.

A subnet can have one or more name servers and host routes. Hosts in this subnet use the name servers. Devices with IP addresses from this subnet, not including the local subnet route, use the host routes.

Specify the ipv6_ra_mode and ipv6_address_mode attributes to create subnets that support IPv6 configurations, such as stateless address autoconfiguration (SLAAC), DHCPv6 stateful, and DHCPv6 stateless configurations.

A subnet can optionally be associated with a network segment when it is created by specifying the segment_id of a valid segment on the specified network. A network with subnets associated in this way is called a routed network. On any given network, all of the subnets must be associated with segments or none of them can be. Neutron enforces this invariant. Currently, routed networks are only supported for provider networks.

Source: https://docs.openstack.org/api-ref/network/v2/index.html#create-subnet

# curl -ks -H 'Content-Type: application/json' -H 'X-Auth-Token: gAAAAA<...>' -d'
{                                    
  "subnet": {
    "enable_dhcp": true,
    "network_id": "c5252a20-9206-4b8e-9a0f-45bd22ee7bc8",
    "dns_nameservers": [
      "10.30.0.27",
      "10.30.0.28"
    ],
    "allocation_pools": [
      {
        "start": "192.168.10.2",
        "end": "192.168.10.254"
      }
    ],
    "ip_version": 4,
    "gateway_ip": "192.168.10.1",
    "cidr": "192.168.10.0/24"
  }
}' https://<node_IP_addr>:9696/v2.0/subnets

# curl -ks -H 'Content-Type: application/json' -H 'X-Auth-Token: gAAAAA<...>' -d '
{
  "subnet": {
    "enable_dhcp": true,
    "network_id": "c5a5d68e-55cd-40b8-a272-3768cbb86bd1",
    "dns_nameservers": [
      "10.30.0.27",
      "10.30.0.28"
    ],
    "allocation_pools": [
      {
        "start": "10.94.139.168",
        "end": "10.94.139.175"
      }
    ],
    "ip_version": 4,
    "gateway_ip": "10.94.0.1",
    "cidr": "10.94.0.0/16"
  }
}' https://<node_IP_addr>:9696/v2.0/subnets

{
  "subnet": {
    "service_types": [],
    "description": "",
    "enable_dhcp": true,
    "tags": [],
    "network_id": "c5252a20-9206-4b8e-9a0f-45bd22ee7bc8",
    "tenant_id": "f5d834d636c642c7bfe8af86139c6f26",
    "created_at": "2020-02-14T13:42:56Z",
    "dns_nameservers": [
      "10.30.0.27",
      "10.30.0.28"
    ],
    "updated_at": "2020-02-14T13:42:56Z",
    "gateway_ip": "192.168.10.1",
    "ipv6_ra_mode": null,
    "allocation_pools": [
      {
        "start": "192.168.10.2",
        "end": "192.168.10.254"
      }
    ],
    "host_routes": [],
    "revision_number": 0,
    "ip_version": 4,
    "ipv6_address_mode": null,
    "cidr": "192.168.10.0/24",
    "project_id": "f5d834d636c642c7bfe8af86139c6f26",
    "id": "aa29d149-b2a4-45a0-8066-dc63fa9c9b77",
    "subnetpool_id": null,
    "name": ""
  }
}

{
  "subnet": {
    "service_types": [],
    "description": "",
    "enable_dhcp": true,
    "tags": [],
    "network_id": "c5a5d68e-55cdl-40b8-a272-3768cbb86bd1",
    "tenant_id": "f5d834d636c642c7bfe8af86139c6f26",
    "created_at": "2020-02-17T11:30:30Z",
    "dns_nameservers": [
      "10.30.0.27",
      "10.30.0.28"
    ],
    "updated_at": "2020-02-17T11:30:30Z",
    "gateway_ip": "10.94.0.1",
    "ipv6_ra_mode": null,
    "allocation_pools": [
      {
        "start": "10.94.139.168",
        "end": "10.94.139.175"
      }
    ],
    "host_routes": [],
    "revision_number": 0,
    "ip_version": 4,
    "ipv6_address_mode": null,
    "cidr": "10.94.0.0/16",
    "project_id": "f5d834d636c642c7bfe8af86139c6f26",
    "id": "5fc296ab-6f00-41ab-914d-0aea9c8da34f",
    "subnetpool_id": null,
    "name": ""
  }
}