# Allocate CIDRs from an IPAM pool
One important feature of IPAM is the ability to allocate and manage IP address space. When creating a VPC, you must specify an IP address CIDR block, which defines the range of IP addresses available for that VPC. IPAM simplifies this process by providing a global view of your entire IP address inventory, helping you strategically assign and reuse IP prefixes across multiple VPCs.
This address space allocation is crucial for ensuring there are no overlapping IP ranges, which could cause routing conflicts and connectivity issues. IPAM also enables you to reserve IP address space for future VPC expansion, avoiding the need for complex renumbering later.
Follow the steps in this section to allocate a CIDR from an IPAM pool to a resource.
**Note**
The terms *provision* and *allocate* are used throughout this user guide and the IPAM console. *Provision* is used when you add a CIDR to an IPAM pool. *Allocate* is used when you associate a CIDR from an IPAM pool with a resource.
You can allocate CIDRs from an IPAM pool in the following ways:
+ Use an AWS service that's integrated with IPAM, such as Amazon VPC, and select the option to use an IPAM pool for the CIDR. IPAM automatically creates the allocation in the pool for you.
+ Manually allocate a CIDR within an IPAM pool to reserve it for later use with an AWS service that's integrated with IPAM, such as Amazon VPC.
This section walks you through both options: how to use the AWS services integrated with IPAM to provision an IPAM pool CIDR, and how to manually reserve IP address space.
**Topics**
+ [Create a VPC that uses an IPAM pool CIDR](create-vpc-ipam.md)
+ [Manually allocate a CIDR to a pool to reserve IP address space](manually-allocate-ipam.md)
# Create a VPC that uses an IPAM pool CIDR
With Amazon Virtual Private Cloud (Amazon VPC), you can launch AWS resources in a logically isolated virtual network that you've defined. This virtual network closely resembles a traditional network that you'd operate in your own data center, with the benefits of using the scalable infrastructure of AWS.
A *virtual private cloud* (VPC) is a virtual network dedicated to your AWS account. It is logically isolated from other virtual networks in the AWS Cloud. You can specify an IP address range for the VPC, add subnets, add gateways, and associate security groups.
Follow the steps in [Create a VPC](https://docs.aws.amazon.com/vpc/latest/userguide/create-vpc.html) in the *Amazon VPC User Guide*. When you reach the step to choose a CIDR for the VPC, you will have an option to use a CIDR from an IPAM pool.
If you choose the option to use an IPAM pool when you create the VPC, AWS allocates a CIDR in the IPAM pool. You can view the allocation in IPAM by choosing a pool in the content pane of the IPAM console and viewing the Resources tab for the pool.
**Note**
For complete instructions using the AWS CLI, including creating a VPC, see the [Tutorials for Amazon VPC IP Address Manager](tutorials-ipam.md) section.
# Manually allocate a CIDR to a pool to reserve IP address space
Follow the steps in this section to manually allocate a CIDR to a pool. You might do this in order to reserve a CIDR within an IPAM pool for later use. You can also reserve space in your IPAM pool to represent an on-premises network. IPAM will manage that reservation for you and indicate if any CIDRs overlap with your on-premises IP space.
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#### [ AWS Management Console ]
**To manually allocate a CIDR**
1. Open the IPAM console at [https://console.aws.amazon.com/ipam/](https://console.aws.amazon.com/ipam/).
1. In the navigation pane, choose **Pools**.
1. By default, the default private scope is selected. If you don’t want to use the default private scope, from the dropdown menu at the top of the content pane, choose the scope you want to use. For more information about scopes, see [How IPAM works](how-it-works-ipam.md).
1. In the content pane, choose a pool.
1. Choose **Actions** > **Create custom allocation**.
1. Choose whether to add a specific CIDR to allocate (for example, `10.0.0.0/24` for IPv4 or `2001:db8::/52` for IPv6) or add a CIDR by size by choosing the netmask length only (for example, `/24` for IPv4 or `/52` for IPv6).
1. Choose **Allocate**.
1. You can view the allocation in IPAM by choosing **Pools** in the navigation pane, choosing a pool, and viewing the **Allocations** tab for the pool.
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#### [ Command line ]
The commands in this section link to the *AWS CLI Command Reference*. The documentation provides detailed descriptions of the options that you can use when you run the commands.
Use the following AWS CLI commands to manually allocate a CIDR to a pool:
1. Get the ID of the IPAM pool that you want to create the allocation in: [describe-ipam-pools](https://docs.aws.amazon.com/cli/latest/reference/ec2/describe-ipam-pools.html).
1. Create the allocation: [allocate-ipam-pool-cidr](https://docs.aws.amazon.com/cli/latest/reference/ec2/allocate-ipam-pool-cidr.html).
1. View the allocation: [get-ipam-pool-allocations](https://docs.aws.amazon.com/cli/latest/reference/ec2/get-ipam-pool-allocations.html).
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To release a manually allocated CIDR, see [Release an allocation](release-alloc-ipam.md).