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Virtual Private Cloud:CreateIpamPoolAllocation

Last Updated:Feb 02, 2026

Creates a custom reserved CIDR block from an IPAM pool.

Operation description

  • Before you create a custom reserved CIDR block, ensure that you have created an IPAM pool and added a CIDR block to it. You can call the CreateIpamPool operation to create an IPAM pool and the AddIpamPoolCidr operation to add a CIDR block to the pool.

  • When you specify the Cidr or CidrMask parameter to create a custom reserved CIDR block, the mask must be within the range specified for the IPAM pool.

  • If an IPAM pool has a region attribute, the request to create a custom reserved CIDR block must be initiated from the region where the pool is located.

  • The custom reserved CIDR block must not conflict with existing CIDR block allocations in the IPAM pool.

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Test

RAM authorization

No authorization for this operation. If you encounter issues with this operation, contact technical support.

Request parameters

Parameter

Type

Required

Description

Example

RegionId

string

Yes

The ID of the region where you want to create the custom reserved CIDR block.

You can call DescribeRegions to obtain the region ID.

cn-hangzhou

IpamPoolId

string

Yes

The ID of the IPAM pool.

ipam-pool-6rcq3tobayc20t****

Cidr

string

No

The CIDR block to allocate from the IPAM pool.

Note

You must specify either the Cidr or CidrMask parameter.

192.168.1.0/24

CidrMask

integer

No

The mask of the CIDR block to allocate from the IPAM pool.

Note

You must specify either the Cidr or CidrMask parameter.

24

DryRun

boolean

No

Specifies whether to perform a dry run. Valid values:

  • true: Sends a check request. The custom reserved CIDR block is not created. The system checks for required parameters, request format, and service limits. If the check fails, an error is returned. If the check passes, the DryRunOperation error code is returned.

  • false (default): Sends a normal request. After the request passes the check, a 2xx HTTP status code is returned and the custom reserved CIDR block is created.

false

ClientToken

string

No

The client token that is used to ensure the idempotence of the request. Generate a value on your client to make sure that the value is unique among different requests. The token can contain only ASCII characters.

Note

If you do not specify this parameter, the system automatically uses the RequestId of the request as the ClientToken. The RequestId may be different for each request.

123e4567-e89b-12d3-a456-426655440000

IpamPoolAllocationDescription

string

No

The description of the custom reserved CIDR block.

The description must be 1 to 256 characters in length. It must start with a letter or a Chinese character and cannot start with http:// or https://. The default value is an empty string.

test description

IpamPoolAllocationName

string

No

The name of the custom reserved CIDR block.

The name must be 1 to 128 characters in length and cannot start with http:// or https://.

test name

Response elements

Element

Type

Description

Example

object

The response parameters.

RequestId

string

The request ID.

CE9CDAE5-341E-5D0B-AC8A-2BAC707D3EB2

IpamPoolAllocationId

string

The ID of the custom reserved CIDR block.

ipam-pool-alloc-112za33e4****

Cidr

string

The allocated CIDR block.

192.168.1.0/24

SourceCidr

string

The source CIDR block.

192.168.0.0/16

Examples

Success response

JSON format

{
  "RequestId": "CE9CDAE5-341E-5D0B-AC8A-2BAC707D3EB2",
  "IpamPoolAllocationId": "ipam-pool-alloc-112za33e4****",
  "Cidr": "192.168.1.0/24",
  "SourceCidr": "192.168.0.0/16"
}

Error codes

HTTP status code

Error code

Error message

Description

400 OperationDenied.ResourceTypeIsNotCustom The operation is not allowed because the resource type is not Custom. The operation is not allowed because the resource type is not Custom.
400 MissingParam.CidrOrCidrMask The CIDR or CIDR Mask must be input. The CIDR or CIDR Mask must be input.
400 OperationDenied.IpamPoolNotInRegion The operation is not allowed because the IPAM pool not in specific region does not support creating VPC or associating CIDR for VPC. The operation is not allowed because the IPAM pool not in specific region does not support creating VPC or associating CIDR for VPC.
400 OperationDenied.RequestRegionInvalid The operation is not allowed because the request is not invoked in the region of the IPAM pool. The operation is not called in the region of the pool.
400 IllegalParam.Cidr The specified CIDR is illegal. The CIDR block is invalid.
400 IllegalParam.CidrMask The specified CidrMask is illegal. Invalid CidrMask.
400 DryRunOperation Request validation has been passed with DryRun flag set.
400 OperationDenied.AvailableCidrInsufficient The operation is not allowed because available CIDR is insufficient. The operation is not allowed because available CIDR is insufficient.
400 OperationDenied.CidrInExcludeCidrs The operation is not allowed because the input CIDR is within the illegal CIDRs. The operation is not allowed because the input CIDR is within the illegal CIDRs.
400 OperationDenied.CidrUnavailableInPool The operation is not allowed because the CIDR is unavailable in the IPAM pool. The operation is not allowed because the CIDR is unavailable in the IPAM pool.
404 ResourceNotFound.IpamPool The dependent IPAM pool is not found. The IPAM pool does not exist.

See Error Codes for a complete list.

Release notes

See Release Notes for a complete list.