This is the new *CloudFormation Template Reference Guide*. Please update your bookmarks and links. For help getting started with CloudFormation, see the [AWS CloudFormation User Guide](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/Welcome.html).
# AWS::EC2::IPAMPrefixListResolver IpamPrefixListResolverRule

Describes a CIDR selection rule.
CIDR selection rules define the business logic for selecting CIDRs from IPAM. If a CIDR matches any of the rules, it will be included. If a rule has multiple conditions, the CIDR has to match every condition of that rule. You can create a prefix list resolver without any CIDR selection rules, but it will generate empty versions (containing no CIDRs) until you add rules.
## Syntax

To declare this entity in your CloudFormation template, use the following syntax:
### JSON

```
{
 "[Conditions](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-conditions)" : {{[ IpamPrefixListResolverRuleCondition, ... ]}},
 "[IpamScopeId](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-ipamscopeid)" : {{String}},
 "[ResourceType](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-resourcetype)" : {{String}},
 "[RuleType](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-ruletype)" : {{String}},
 "[StaticCidr](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-staticcidr)" : {{String}}
}
```
### YAML

```
 [Conditions](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-conditions): {{
 - IpamPrefixListResolverRuleCondition}}
 [IpamScopeId](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-ipamscopeid): {{String}}
 [ResourceType](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-resourcetype): {{String}}
 [RuleType](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-ruletype): {{String}}
 [StaticCidr](#cfn-ec2-ipamprefixlistresolver-ipamprefixlistresolverrule-staticcidr): {{String}}
```
## Properties

`Conditions` 
The conditions that determine which CIDRs are selected by this rule. Conditions specify criteria such as resource type, tags, account IDs, and Regions. 
*Required*: No 
*Type*: Array of [IpamPrefixListResolverRuleCondition](aws-properties-ec2-ipamprefixlistresolver-ipamprefixlistresolverrulecondition.md) 
*Update requires*: [No interruption](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)
`IpamScopeId` 
The ID of the IPAM scope from which to select CIDRs. This determines whether to select from public or private IP address space. 
*Required*: No 
*Type*: String 
*Update requires*: [No interruption](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)
`ResourceType` 
For rules of type `ipam-resource-cidr`, this is the resource type. 
*Required*: No 
*Type*: String 
*Allowed values*: `vpc | subnet | eip | public-ipv4-pool` 
*Update requires*: [No interruption](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)
`RuleType` 
The type of CIDR selection rule. Valid values include `static-cidr` for specifying a fixed CIDR, `ipam-resource-cidr` for CIDRs from resources such as VPCs and subnets, and `ipam-pool-cidr` for CIDRs from IPAM pools. 
*Required*: Yes 
*Type*: String 
*Allowed values*: `static-cidr | ipam-resource-cidr | ipam-pool-cidr` 
*Update requires*: [No interruption](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)
`StaticCidr` 
A fixed CIDR that does not change. This property can only be specified for rules of type `static-cidr`. 
*Required*: No 
*Type*: String 
*Update requires*: [No interruption](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html#update-no-interrupt)</div><div class="naked_ctrl">
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