> For the complete documentation index, see [llms.txt](https://docs.console.zenlayer.com/api-reference/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.console.zenlayer.com/api-reference/zec/vpc-network/modifysubnetstacktype.md).
# ModifySubnetStackType
## 1. API Description
This API (ModifySubnetStackType) is used to modify the IP stack type of a subnet (IPv4 / IPv4\_IPv6 / IPv6). When changing to dual stack or IPv6 only, the IPv6 type and the corresponding CIDR block must be configured.
{% hint style="info" %}
**Notes**
* Switching from `IPv4` to `IPv4_IPv6` is supported: after the switch, an IPv6 CIDR block is obtained.
* Switching from `IPv4_IPv6` to `IPv4` (disabling IPv6) is supported: both public and private IPv6 subnets are supported. Before disabling it, make sure that no IPv6 address in the subnet is in use — the IPv6 addresses of network interfaces are deleted through [UnassignNetworkInterfaceIpv6](/api-reference/zec/public-ipv6/unassignnetworkinterfaceipv6.md), and the IPv6 VIPs of load balancers are deleted through [DeleteIpv6Addresses](/api-reference/zec/public-ipv6/deleteipv6addresses.md).
{% endhint %}
## 2. Input Parameters
The following request parameter list only provides API request parameters.
| Parameter Name | Required | Type | Description |
| --------------- | -------- | ---------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| subnetId | Yes | String | ID of the subnet to be operated on.
It can be obtained by calling DescribeSubnets.
|
| stackType | Yes | [SubnetStackType](/api-reference/zec/datastructure.md#subnetstacktype) | Subnet stack type.
IPv4\_IPv6: public IPv6 is enabled; whether it is public or private is specified by ipv6Type.
IPv4: IPv6 is disabled. Before disabling it, make sure that no IPv6 address in the subnet is in use: the IPv6 addresses of network interfaces are deleted through UnassignNetworkInterfaceIpv6, and the IPv6 VIPs of load balancers are deleted through DeleteIpv6Addresses.
|
| ipv6Type | No | [IPv6Type](/api-reference/zec/datastructure.md#ipv6type) | Type of the IPv6 address.
Required when stackType is IPv4\_IPv6.
|
| ipv6CidrBlockId | No | String | ID of the public IPv6 CIDR block.
This field can only be specified when ipv6Type is Public.
If not specified, it will be allocated from the system's default IP pool.
|
| ipv6MaskLength | No | Integer | The size of the IPv6 CIDR prefix assigned to the instance.
This parameter must be used together with the ipv6CidrBlockId parameter.
The default value is 96 if not explicitly provided.
The minimum value must be greater than or equal to the prefix of the specified ipv6CidrBlockId, and the maximum value cannot exceed 96.
Value range: \[-, 96]
|
## 3. Output Parameters
| Parameter Name | Type | Description |
| -------------- | ------ | --------------------------------------------------------------------------------------------------------------------- |
| requestId | String | The unique request ID, which is returned for each request.
RequestId is required for locating a problem.
|
| ipv6CidrBlock | String | IPv6 CIDR block of subnet. |
## 4. Code Example
{% tabs %}
{% tab title="Example" %}
**1. Modify the subnet stack type: IPv4 → IPv4\_IPv6, specifying private IPv6.**
```json
POST /api/v2/zec HTTP/1.1
Host: console.zenlayer.com
Content-Type: application/json
X-ZC-Action: ModifySubnetStackType
Request：
{
"subnetId": "XXX",
"stackType": "IPv4_IPv6",
"ipv6Type": "Private"
}
Response：
{
"requestId": "T05992D0C-7E8B-4047-B0C0-780F2CD549D3",
"response": {
"requestId": "T05992D0C-7E8B-4047-B0C0-780F2CD549D3",
"ipv6CidrBlock": "f0xxxx:xx:xxx::/64"
}
}
```
**2. Disable public IPv6 for the subnet: IPv4\_IPv6 → IPv4.**
```json
POST /api/v2/zec HTTP/1.1
Host: console.zenlayer.com
Content-Type: application/json
X-ZC-Action: ModifySubnetStackType
Request：
{
"subnetId": "XXX",
"stackType": "IPv4"
}
Response：
{
"requestId": "T05992D0C-7E8B-4047-B0C0-780F2CD549D3",
"response": {
"requestId": "T05992D0C-7E8B-4047-B0C0-780F2CD549D3"
}
}
```
{% endtab %}
{% endtabs %}
## 5. Developer Resources
Zenlayer Cloud API 2.0 integrates [SDKs](/api-reference/api-introduction/toolkit/api-sdk.md)，to make it easier for you to call APIs. More programming languages will be supported.
## 6. Error Codes
The following only lists the error codes related to the API business logic. For other error codes, see [Common Error Codes](/api-reference/api-introduction/instruction/commonerrorcode.md).
| HTTP Status Code | Error Code | Description |
| ---------------- | -------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| 400 | INVALID\_CIDR\_BLOCK\_STATUS | The CIDR block state is invalid. |
| 404 | INVALID\_CIDR\_IPV6\_NOT\_FOUND | The IPv6 CIDR block does not exist. |
| 400 | INVALID\_CIDR\_REGION\_MISMATCH | The subnet region does not match the IPv6 CIDR block region. |
| 400 | INVALID\_MASK\_LENGTH | The IPv6 address mask length must be greater than or equal to the subnet IPv6 prefix length. |
| 400 | INVALID\_SUBNET\_HAS\_IPV6\_ALLOCATED | The subnet still has vNICs or load balancers holding IPv6 addresses. Call UnassignNetworkInterfaceIpv6 for the vNICs and DeleteIpv6Addresses for the load balancer VIPs first. |
| 404 | INVALID\_SUBNET\_NOT\_FOUND | Subnet does not exist. |
| 404 | INVALID\_VPC\_NOT\_FOUND | The global VPC does not exist. |
| 404 | INVALID\_ZONE\_NOT\_FOUND | Region does not exist. |
| 400 | OPERATION\_DENIED\_NO\_AVAILABLE\_CIDR | No available CIDR block. |
| 400 | OPERATION\_DENIED\_REGION\_NOT\_SUPPORT\_PUB\_IPV6 | Public IPv6 is not supported in the specified region. |
| 400 | OPERATION\_DENIED\_SUBNET\_TYPE\_NOT\_SUPPORT | Operations on subnets with such IP stack type is not supported. |
| 400 | OPERATION\_DENIED\_VPC\_NOT\_SUPPORT\_PRI\_IPV6 | Private IPv6 is not supported for the specified global VPC. |