# Peer with a VPC in another AWS account
Peer with a VPC in another account

You can peer with a Virtual Private Cloud (VPC) in another AWS account by using [https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-ec2-vpcpeeringconnection.html](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-ec2-vpcpeeringconnection.html). This creates a networking connection between two VPCs that enables you to route traffic between them so they can communicate as if they were within the same network. A VPC peering connection can help facilitate data access and data transfer.

To establish a VPC peering connection, you need to authorize two separate AWS accounts within a single CloudFormation stack.

For more information about VPC peering and its limitations, see the [Amazon VPC Peering Guide](https://docs.aws.amazon.com/vpc/latest/peering/). 

## Prerequisites


1. You need a peer VPC ID, a peer AWS account ID, and a [cross-account access role](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_common-scenarios_aws-accounts.html) for the peering connection. 
**Note**  
This walkthrough refers to two accounts: First is an account that allows cross-account peering (the *accepter account*). Second is an account that requests the peering connection (the *requester account*).

1. To accept the VPC peering connection, the cross-account access role must be assumable by you. The resource behaves the same way as a VPC peering connection resource in the same account. For information about how an IAM administrator grants permissions to assume the cross-account role, see [Grant a user permissions to switch roles](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_roles_use_permissions-to-switch.html) in the *IAM User Guide*.

## Step 1: Create a VPC and a cross-account role


In this step, you'll create the VPC and role in the *accepter account*.

**To create a VPC and a cross-account access role**

1. Sign in to the AWS Management Console and open the CloudFormation console at [https://console.aws.amazon.com/cloudformation](https://console.aws.amazon.com/cloudformation/).

1. From the **Stacks** page, choose **Create stack** at top right, and then choose **With new resources (standard)**.

1. For **Prerequisite - Prepare template**, choose **Choose an existing template** and then **Upload a template file**, **Choose file**.

1. Open a text editor on your local machine and add one of the following templates. Save the file and return to the console to select it as the template file.  
**Example JSON**  

   ```
   {
     "AWSTemplateFormatVersion": "2010-09-09",
     "Description": "Create a VPC and an assumable role for cross account VPC peering.",
     "Parameters": {
       "PeerRequesterAccountId": {
         "Type": "String"
       }
     },
     "Resources": {
       "vpc": {
         "Type": "AWS::EC2::VPC",
         "Properties": {
           "CidrBlock": "10.1.0.0/16",
           "EnableDnsSupport": false,
           "EnableDnsHostnames": false,
           "InstanceTenancy": "default"
         }
       },
       "peerRole": {
         "Type": "AWS::IAM::Role",
         "Properties": {
           "AssumeRolePolicyDocument": {
             "Statement": [
               {
                 "Principal": {
                   "AWS": {
                     "Ref": "PeerRequesterAccountId"
                   }
                 },
                 "Action": [
                   "sts:AssumeRole"
                 ],
                 "Effect": "Allow"
               }
             ]
           },
           "Path": "/",
           "Policies": [
             {
               "PolicyName": "root",
               "PolicyDocument": {
                 "Version": "2012-10-17",		 	 	 
                 "Statement": [
                   {
                     "Effect": "Allow",
                     "Action": "ec2:AcceptVpcPeeringConnection",
                     "Resource": "*"
                   }
                 ]
               }
             }
           ]
         }
       }
     },
     "Outputs": {
       "VPCId": {
         "Value": {
           "Ref": "vpc"
         }
       },
       "RoleARN": {
         "Value": {
           "Fn::GetAtt": [
             "peerRole",
             "Arn"
           ]
         }
       }
     }
   }
   ```  
**Example YAML**  

   ```
   AWSTemplateFormatVersion: 2010-09-09
   Description: Create a VPC and an assumable role for cross account VPC peering.
   Parameters:
     PeerRequesterAccountId:
       Type: String
   Resources:
     vpc:
       Type: AWS::EC2::VPC
       Properties:
         CidrBlock: 10.1.0.0/16
         EnableDnsSupport: false
         EnableDnsHostnames: false
         InstanceTenancy: default
     peerRole:
       Type: AWS::IAM::Role
       Properties:
         AssumeRolePolicyDocument:
           Statement:
             - Principal:
                 AWS: !Ref PeerRequesterAccountId
               Action:
                 - 'sts:AssumeRole'
               Effect: Allow
         Path: /
         Policies:
           - PolicyName: root
             PolicyDocument:
               Version: 2012-10-17 		 	 	 
               Statement:
                 - Effect: Allow
                   Action: 'ec2:AcceptVpcPeeringConnection'
                   Resource: '*'
   Outputs:
     VPCId:
       Value: !Ref vpc
     RoleARN:
       Value: !GetAtt 
         - peerRole
         - Arn
   ```

1. Choose **Next**.

1. Give the stack a name (for example, **VPC-owner**), and then enter the AWS account ID of the *requester account* in the **PeerRequesterAccountId** field.

1. Accept the defaults, and then choose **Next**.

1. Choose **I acknowledge that CloudFormation might create IAM resources**, and then choose **Create stack**.

## Step 2: Create a template that includes `AWS::EC2::VPCPeeringConnection`


Now that you've created the VPC and cross-account role, you can peer with the VPC using another AWS account (the *requester account*).

**To create a template that includes the [AWS::EC2::VPCPeeringConnection](https://docs.aws.amazon.com/AWSCloudFormation/latest/TemplateReference/aws-resource-ec2-vpcpeeringconnection.html) resource**

1. Go back to the CloudFormation console home page.

1. From the **Stacks** page, choose **Create stack** at top right, and then choose **With new resources (standard)**.

1. For **Prerequisite - Prepare template**, choose **Choose an existing template** and then **Upload a template file**, **Choose file**.

1. Open a text editor on your local machine and add one of the following templates. Save the file and return to the console to select it as the template file.  
**Example JSON**  

   ```
   {
     "AWSTemplateFormatVersion": "2010-09-09",
     "Description": "Create a VPC and a VPC Peering connection using the PeerRole to accept.",
     "Parameters": {
       "PeerVPCAccountId": {
         "Type": "String"
       },
       "PeerVPCId": {
         "Type": "String"
       },
       "PeerRoleArn": {
         "Type": "String"
       }
     },
     "Resources": {
       "vpc": {
         "Type": "AWS::EC2::VPC",
         "Properties": {
           "CidrBlock": "10.2.0.0/16",
           "EnableDnsSupport": false,
           "EnableDnsHostnames": false,
           "InstanceTenancy": "default"
         }
       },
       "vpcPeeringConnection": {
         "Type": "AWS::EC2::VPCPeeringConnection",
         "Properties": {
           "VpcId": {
             "Ref": "vpc"
           },
           "PeerVpcId": {
             "Ref": "PeerVPCId"
           },
           "PeerOwnerId": {
             "Ref": "PeerVPCAccountId"
           },
           "PeerRoleArn": {
             "Ref": "PeerRoleArn"
           }
         }
       }
     },
     "Outputs": {
       "VPCId": {
         "Value": {
           "Ref": "vpc"
         }
       },
       "VPCPeeringConnectionId": {
         "Value": {
           "Ref": "vpcPeeringConnection"
         }
       }
     }
   }
   ```  
**Example YAML**  

   ```
   AWSTemplateFormatVersion: 2010-09-09
   Description: Create a VPC and a VPC Peering connection using the PeerRole to accept.
   Parameters:
     PeerVPCAccountId:
       Type: String
     PeerVPCId:
       Type: String
     PeerRoleArn:
       Type: String
   Resources:
     vpc:
       Type: AWS::EC2::VPC
       Properties:
         CidrBlock: 10.2.0.0/16
         EnableDnsSupport: false
         EnableDnsHostnames: false
         InstanceTenancy: default
     vpcPeeringConnection:
       Type: AWS::EC2::VPCPeeringConnection
       Properties:
         VpcId: !Ref vpc
         PeerVpcId: !Ref PeerVPCId
         PeerOwnerId: !Ref PeerVPCAccountId
         PeerRoleArn: !Ref PeerRoleArn
   Outputs:
     VPCId:
       Value: !Ref vpc
     VPCPeeringConnectionId:
       Value: !Ref vpcPeeringConnection
   ```

1. Choose **Next**.

1. Give the stack a name (for example, **VPC-peering-connection**).

1. Accept the defaults, and then choose **Next**.

1. Choose **I acknowledge that CloudFormation might create IAM resources**, and then choose **Create stack**.

## Create a template with a highly restrictive policy


You might want to create a highly restrictive policy for peering your VPC with another AWS account. 

The following example template shows how to change the VPC peer owner template (the *accepter account* created in Step 1 above) so that it's more restrictive.

**Example JSON**  

```
{
  "AWSTemplateFormatVersion":"2010-09-09",
  "Description":"Create a VPC and an assumable role for cross account VPC peering.",
  "Parameters":{
    "PeerRequesterAccountId":{
      "Type":"String"
    }
  },
  "Resources":{
    "peerRole":{
      "Type":"AWS::IAM::Role",
      "Properties":{
        "AssumeRolePolicyDocument":{
          "Statement":[
            {
              "Action":[
                "sts:AssumeRole"
              ],
              "Effect":"Allow",
              "Principal":{
                "AWS":{
                  "Ref":"PeerRequesterAccountId"
                }
              }
            }
          ]
        },
        "Path":"/",
        "Policies":[
          {
            "PolicyDocument":{
              "Statement":[
                {
                  "Action":"ec2:acceptVpcPeeringConnection",
                  "Effect":"Allow",
                  "Resource":{
                    "Fn::Sub":"arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:vpc/${vpc}"
                  }
                },
                {
                  "Action":"ec2:acceptVpcPeeringConnection",
                  "Condition":{
                    "StringEquals":{
                      "ec2:AccepterVpc":{
                        "Fn::Sub":"arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:vpc/${vpc}"
                      }
                    }
                  },
                  "Effect":"Allow",
                  "Resource":{
                    "Fn::Sub":"arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:vpc-peering-connection/*"
                  }
                }
              ],
              "Version":"2012-10-17" 		 	 	 
            },
            "PolicyName":"root"
          }
        ]
      }
    },
    "vpc":{
      "Type":"AWS::EC2::VPC",
      "Properties":{
        "CidrBlock":"10.1.0.0/16",
        "EnableDnsHostnames":false,
        "EnableDnsSupport":false,
        "InstanceTenancy":"default"
      }
    }
  },
  "Outputs":{
    "RoleARN":{
      "Value":{
        "Fn::GetAtt":[
          "peerRole",
          "Arn"
        ]
      }
    },
    "VPCId":{
      "Value":{
        "Ref":"vpc"
      }
    }
  }
}
```

**Example YAML**  

```
AWSTemplateFormatVersion: 2010-09-09
Description: Create a VPC and an assumable role for cross account VPC peering.
Parameters:
  PeerRequesterAccountId:
    Type: String
Resources:
  peerRole:
    Type: AWS::IAM::Role
    Properties:
      AssumeRolePolicyDocument:
        Statement:
          - Action:
              - 'sts:AssumeRole'
            Effect: Allow
            Principal:
              AWS:
                Ref: PeerRequesterAccountId
      Path: /
      Policies:
        - PolicyDocument:
            Statement:
              - Action: 'ec2:acceptVpcPeeringConnection'
                Effect: Allow
                Resource:
                  'Fn::Sub': 'arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:vpc/${vpc}'
              - Action: 'ec2:acceptVpcPeeringConnection'
                Condition:
                  StringEquals:
                    'ec2:AccepterVpc':
                      'Fn::Sub': 'arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:vpc/${vpc}'
                Effect: Allow
                Resource:
                  'Fn::Sub': >-
                    arn:aws:ec2:${AWS::Region}:${AWS::AccountId}:vpc-peering-connection/*
            Version: 2012-10-17 		 	 	 
          PolicyName: root
  vpc:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.1.0.0/16
      EnableDnsHostnames: false
      EnableDnsSupport: false
      InstanceTenancy: default
Outputs:
  RoleARN:
    Value:
      'Fn::GetAtt':
        - peerRole
        - Arn
  VPCId:
    Value:
      Ref: vpc
```

To access the VPC, you can use the same requester template as in Step 2 above.

For more information, see [Identity and access management for VPC peering](https://docs.aws.amazon.com/vpc/latest/peering/security-iam.html) in the *Amazon VPC Peering Guide*.