Create Subnet

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

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 SLAAC, DHCPv6 stateful, and DHCPv6 stateless configurations.

Optionally, a subnet can be associated with a network segment when it is created by specifying the segment_id of a valid segment on the specified network (routed networks).

info

Source: create-subnet

Request

Body parameters

Name	In	Type	Description
`subnet`	body	object	A subnet object.
`tenant_id` (Optional)	body	string	The ID of the project that owns the resource. Admin/advsvc can specify a different project.
`project_id` (Optional)	body	string	The ID of the project that owns the resource. Admin/advsvc can specify a different project.
`name` (Optional)	body	string	Human-readable name of the subnet.
`description` (Optional)	body	string	Human-readable description.
`enable_dhcp` (Optional)	body	boolean	Whether DHCP is enabled for the subnet. Default: `true`.
`network_id`	body	string	The ID of the network to which the subnet belongs.
`dns_nameservers` (Optional)	body	array	List of DNS name servers associated with the subnet.
`allocation_pools` (Optional)	body	array	Allocation pools with start and end IP addresses for this subnet. If omitted, pools are auto-allocated (excluding gateway).
`host_routes` (Optional)	body	array	Additional routes. Each item has `destination` and `nexthop`.
`ip_version`	body	integer	IP protocol version. `4` or `6`.
`gateway_ip` (Optional)	body	string	Gateway IP of this subnet. Use `null` to create without a gateway. If omitted, an address is allocated from the CIDR.
`cidr`	body	string	The CIDR of the subnet.
`prefixlen` (Optional)	body	integer	Prefix length to use for allocation from a subnet pool.
`ipv6_address_mode` (Optional)	body	string	IPv6 address assignment mode: `slaac`, `dhcpv6-stateful`, `dhcpv6-stateless`.
`ipv6_ra_mode` (Optional)	body	string	IPv6 router advertisement mode: `slaac`, `dhcpv6-stateful`, `dhcpv6-stateless`.
`segment_id` (Optional)	body	string	The ID of a network segment the subnet is associated with.
`subnetpool_id` (Optional)	body	string	The ID of the subnet pool associated with the subnet.
`use_default_subnetpool` (Optional)	body	boolean	Whether to allocate this subnet from the default subnet pool.
`service_types` (Optional)	body	array	Service types associated with the subnet.
`dns_publish_fixed_ip` (Optional)	body	boolean	Whether to publish DNS records for IPs from this subnet. Default: `false`.

Example requests

Using `curl` (create a subnet on a private network)

curl -ks -H 'Content-Type: application/json' \
  -H 'X-Auth-Token: gAAAAA<...>' -d '
{                                    
  "subnet": {
    "enable_dhcp": true,
    "network_id": "170546a1-a70a-40af-93e2-9261c7c05b77",
    "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://api.vietnix.cloud:9696/v2.0/subnets

Using HTTP request

POST https://api.vietnix.cloud:9696/v2.0/subnets

Response

Response parameters

Name	Type	Description
`subnet`	object	A subnet object.
`id`	string	The ID of the subnet.
`tenant_id`	string	The ID of the project.
`project_id`	string	The ID of the project.
`name`	string	Human-readable name of the resource.
`description`	string	Human-readable description.
`enable_dhcp`	boolean	Whether DHCP is enabled for the subnet.
`network_id`	string	The ID of the network to which the subnet belongs.
`dns_nameservers`	array	List of DNS name servers associated with the subnet.
`allocation_pools`	array	Allocation pools with start and end IP addresses.
`host_routes`	array	Additional routes with `destination` and `nexthop`.
`ip_version`	integer	IP protocol version. `4` or `6`.
`gateway_ip`	string	Gateway IP of this subnet, or `null`.
`cidr`	string	The CIDR of the subnet.
`created_at`	string	Creation time (ISO 8601).
`updated_at`	string	Last update time (ISO 8601) or `null`.
`ipv6_address_mode`	string	IPv6 address mode or `null`.
`ipv6_ra_mode`	string	IPv6 router advertisement mode or `null`.
`revision_number`	integer	Revision number.
`segment_id`	string	Associated network segment ID, if any.
`subnetpool_id`	string	Subnet pool ID, if any.
`service_types`	array	Service types associated with the subnet.
`tags`	array	List of tags on the resource.
`dns_publish_fixed_ip`	boolean	Whether to publish DNS records for IPs from this subnet.

Sample responses

Subnet for a private network

{
    "subnet": {
        "id": "d3f93e1c-f59d-40f8-a46c-ea6285f3a069",
        "name": "",
        "tenant_id": "f33507157a634f1cac71e06a70fb558e",
        "network_id": "170546a1-a70a-40af-93e2-9261c7c05b77",
        "ip_version": 4,
        "subnetpool_id": null,
        "enable_dhcp": true,
        "ipv6_ra_mode": null,
        "ipv6_address_mode": null,
        "gateway_ip": "192.168.10.1",
        "cidr": "192.168.10.0/24",
        "allocation_pools": [
            {
                "start": "192.168.10.2",
                "end": "192.168.10.254"
            }
        ],
        "host_routes": [],
        "dns_nameservers": [
            "10.30.0.27",
            "10.30.0.28"
        ],
        "description": "",
        "service_types": [],
        "tags": [],
        "created_at": "2025-09-23T07:00:56Z",
        "updated_at": "2025-09-23T07:00:56Z",
        "revision_number": 0,
        "project_id": "f33507157a634f1cac71e06a70fb558e"
    }
}

Status codes

Success

Status Code	Description
201 - Created	Resource was created and is ready to use.

Error

Status Code	Description
400 - Bad Request	Some content in the request was invalid.
401 - Unauthorized	User must authenticate before making a request.
403 - Forbidden	Policy does not allow current user to do this operation.
404 - Not Found	The requested resource could not be found.
409 - Conflict	This operation conflicted with another operation on this resource.

Request​

Body parameters​

Example requests​

Using curl (create a subnet on a private network)​

Using HTTP request​

Response​

Response parameters​

Sample responses​

Subnet for a private network​

Status codes​

Success​

Error​